diff --git a/Avalonia.sln b/Avalonia.sln
index 009d7b19bd..9917547a67 100644
--- a/Avalonia.sln
+++ b/Avalonia.sln
@@ -201,19 +201,20 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Controls.DataGrid"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Dialogs", "src\Avalonia.Dialogs\Avalonia.Dialogs.csproj", "{4D55985A-1EE2-4F25-AD39-6EA8BC04F8FB}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.FreeDesktop", "src\Avalonia.FreeDesktop\Avalonia.FreeDesktop.csproj", "{4D36CEC8-53F2-40A5-9A37-79AAE356E2DA}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.FreeDesktop", "src\Avalonia.FreeDesktop\Avalonia.FreeDesktop.csproj", "{4D36CEC8-53F2-40A5-9A37-79AAE356E2DA}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.Controls.DataGrid.UnitTests", "tests\Avalonia.Controls.DataGrid.UnitTests\Avalonia.Controls.DataGrid.UnitTests.csproj", "{351337F5-D66F-461B-A957-4EF60BDB4BA6}"
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NativeEmbedSample", "samples\interop\NativeEmbedSample\NativeEmbedSample.csproj", "{3C84E04B-36CF-4D0D-B965-C26DD649D1F3}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Controls.DataGrid.UnitTests", "tests\Avalonia.Controls.DataGrid.UnitTests\Avalonia.Controls.DataGrid.UnitTests.csproj", "{351337F5-D66F-461B-A957-4EF60BDB4BA6}"
+EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
 		src\Shared\RenderHelpers\RenderHelpers.projitems*{3c4c0cb4-0c0f-4450-a37b-148c84ff905f}*SharedItemsImports = 13
-		src\Shared\RenderHelpers\RenderHelpers.projitems*{3e908f67-5543-4879-a1dc-08eace79b3cd}*SharedItemsImports = 4
+		src\Shared\RenderHelpers\RenderHelpers.projitems*{3e908f67-5543-4879-a1dc-08eace79b3cd}*SharedItemsImports = 5
 		src\Shared\PlatformSupport\PlatformSupport.projitems*{4488ad85-1495-4809-9aa4-ddfe0a48527e}*SharedItemsImports = 4
 		src\Shared\PlatformSupport\PlatformSupport.projitems*{7b92af71-6287-4693-9dcb-bd5b6e927e23}*SharedItemsImports = 4
-		src\Shared\RenderHelpers\RenderHelpers.projitems*{7d2d3083-71dd-4cc9-8907-39a0d86fb322}*SharedItemsImports = 4
-		tests\Avalonia.RenderTests\Avalonia.RenderTests.projitems*{dabfd304-d6a4-4752-8123-c2ccf7ac7831}*SharedItemsImports = 4
+		src\Shared\RenderHelpers\RenderHelpers.projitems*{7d2d3083-71dd-4cc9-8907-39a0d86fb322}*SharedItemsImports = 5
+		src\Shared\PlatformSupport\PlatformSupport.projitems*{88060192-33d5-4932-b0f9-8bd2763e857d}*SharedItemsImports = 5
 		src\Shared\PlatformSupport\PlatformSupport.projitems*{e4d9629c-f168-4224-3f51-a5e482ffbc42}*SharedItemsImports = 13
 	EndGlobalSection
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 603308ef9a..1cde4ac8b8 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -14,7 +14,7 @@ jobs:
     displayName: 'Install Nuke'
     inputs:
       script: |
-         dotnet tool install --global Nuke.GlobalTool --version 0.12.3
+         dotnet tool install --global Nuke.GlobalTool --version 0.24.0
   - task: CmdLine@2
     displayName: 'Run Nuke'
     inputs:
@@ -34,9 +34,17 @@ jobs:
   pool:
     vmImage: 'macOS-10.14'
   steps:
-  - task: DotNetCoreInstaller@0
+  - task: UseDotNet@2
+    displayName: 'Use .NET Core SDK 3.1.101'
     inputs:
-      version: '2.1.403'
+      packageType: sdk
+      version: 3.1.101
+
+  - task: UseDotNet@2
+    displayName: 'Use .NET Core Runtime 3.1.1'
+    inputs:
+      packageType: runtime
+      version: 3.1.1
 
   - task: CmdLine@2
     displayName: 'Install Mono 5.18'
@@ -60,13 +68,13 @@ jobs:
     inputs:
       script: |
         brew update
-        brew install castxml
+        brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/8a004a91a7fcd3f6620d5b01b6541ff0a640ffba/Formula/castxml.rb
 
   - task: CmdLine@2
     displayName: 'Install Nuke'
     inputs:
       script: |
-       dotnet tool install --global Nuke.GlobalTool --version 0.12.3 
+       dotnet tool install --global Nuke.GlobalTool --version 0.24.0
 
   - task: CmdLine@2
     displayName: 'Run Nuke'
@@ -108,7 +116,7 @@ jobs:
     displayName: 'Install Nuke'
     inputs:
       script: |
-       dotnet tool install --global Nuke.GlobalTool --version 0.12.3 
+       dotnet tool install --global Nuke.GlobalTool --version 0.24.0 
 
   - task: CmdLine@2
     displayName: 'Run Nuke'
@@ -134,4 +142,3 @@ jobs:
       pathToPublish: '$(Build.SourcesDirectory)/artifacts/zip'
       artifactName: 'Samples'
     condition: succeeded()
-
diff --git a/build/SharedVersion.props b/build/SharedVersion.props
index 1294b5f6f2..5b1d2e4f94 100644
--- a/build/SharedVersion.props
+++ b/build/SharedVersion.props
@@ -2,7 +2,7 @@
   xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Product>Avalonia</Product>
-    <Version>0.9.3</Version>
+    <Version>0.9.10-preview</Version>
     <Copyright>Copyright 2020 &#169; The AvaloniaUI Project</Copyright>
     <PackageProjectUrl>https://avaloniaui.net</PackageProjectUrl>
     <RepositoryUrl>https://github.com/AvaloniaUI/Avalonia/</RepositoryUrl>
diff --git a/global.json b/global.json
index 1e599211d4..a3fdca9bed 100644
--- a/global.json
+++ b/global.json
@@ -1,4 +1,7 @@
 {
+	"sdk": {
+		"version": "3.1.101"
+	},
     "msbuild-sdks": {
         "Microsoft.Build.Traversal": "1.0.43",
         "MSBuild.Sdk.Extras": "2.0.46",
diff --git a/native/Avalonia.Native/src/OSX/platformthreading.mm b/native/Avalonia.Native/src/OSX/platformthreading.mm
index e7abedae51..ed00f8c5e1 100644
--- a/native/Avalonia.Native/src/OSX/platformthreading.mm
+++ b/native/Avalonia.Native/src/OSX/platformthreading.mm
@@ -157,11 +157,14 @@ NSArray<NSString*>* _modes;
 
 -(void) perform
 {
+    ComPtr<IAvnSignaledCallback> cb;
     @synchronized (self) {
         _signaled  = false;
-        if(_parent != NULL && _parent->SignaledCallback != NULL)
-            _parent->SignaledCallback->Signaled(0, false);
+        if(_parent != NULL)
+            cb = _parent->SignaledCallback;
     }
+    if(cb != nullptr)
+        cb->Signaled(0, false);
 }
 
 -(void) setParent:(PlatformThreadingInterface *)parent
diff --git a/native/Avalonia.Native/src/OSX/window.mm b/native/Avalonia.Native/src/OSX/window.mm
index e723a58c92..c9936fef01 100644
--- a/native/Avalonia.Native/src/OSX/window.mm
+++ b/native/Avalonia.Native/src/OSX/window.mm
@@ -31,9 +31,11 @@ public:
     AvnPoint lastPositionSet;
     NSString* _lastTitle;
     IAvnAppMenu* _mainMenu;
+    bool _shown;
     
     WindowBaseImpl(IAvnWindowBaseEvents* events, IAvnGlContext* gl)
     {
+        _shown = false;
         _mainMenu = nullptr;
         BaseEvents = events;
         _glContext = gl;
@@ -116,6 +118,8 @@ public:
             
             [Window setTitle:_lastTitle];
             [Window setTitleVisibility:NSWindowTitleVisible];
+            
+            _shown = true;
         
             return S_OK;
         }
@@ -409,6 +413,7 @@ protected:
         [Window setStyleMask:GetStyle()];
     }
     
+public:
     virtual void OnResized ()
     {
         
@@ -435,6 +440,7 @@ private:
     ComPtr<IAvnWindowEvents> WindowEvents;
     WindowImpl(IAvnWindowEvents* events, IAvnGlContext* gl) : WindowBaseImpl(events, gl)
     {
+        _lastWindowState = Normal;
         WindowEvents = events;
         [Window setCanBecomeKeyAndMain];
         [Window disableCursorRects];
@@ -448,7 +454,7 @@ private:
                 [[Window parentWindow] removeChildWindow:Window];
             WindowBaseImpl::Show();
             
-            return SetWindowState(Normal);
+            return SetWindowState(_lastWindowState);
         }
     }
     
@@ -599,57 +605,63 @@ private:
         {
             _lastWindowState = state;
             
-            switch (state) {
-                case Maximized:
-                    lastPositionSet.X = 0;
-                    lastPositionSet.Y = 0;
-                    
-                    if([Window isMiniaturized])
-                    {
-                        [Window deminiaturize:Window];
-                    }
-                    
-                    if(!IsZoomed())
-                    {
-                        DoZoom();
-                    }
-                    break;
-                    
-                case Minimized:
-                    [Window miniaturize:Window];
-                    break;
-                    
-                default:
-                    if([Window isMiniaturized])
-                    {
-                        [Window deminiaturize:Window];
-                    }
-                    
-                    if(IsZoomed())
-                    {
-                        DoZoom();
-                    }
-                    break;
+            if(_shown)
+            {
+                switch (state) {
+                    case Maximized:
+                        lastPositionSet.X = 0;
+                        lastPositionSet.Y = 0;
+                        
+                        if([Window isMiniaturized])
+                        {
+                            [Window deminiaturize:Window];
+                        }
+                        
+                        if(!IsZoomed())
+                        {
+                            DoZoom();
+                        }
+                        break;
+                        
+                    case Minimized:
+                        [Window miniaturize:Window];
+                        break;
+                        
+                    default:
+                        if([Window isMiniaturized])
+                        {
+                            [Window deminiaturize:Window];
+                        }
+                        
+                        if(IsZoomed())
+                        {
+                            DoZoom();
+                        }
+                        break;
+                }
             }
             
             return S_OK;
         }
     }
-    
-protected:
+
     virtual void OnResized () override
     {
-        auto windowState = [Window isMiniaturized] ? Minimized
-        : (IsZoomed() ? Maximized : Normal);
-        
-        if (windowState != _lastWindowState)
+        if(_shown)
         {
-            _lastWindowState = windowState;
+            auto windowState = [Window isMiniaturized] ? Minimized
+            : (IsZoomed() ? Maximized : Normal);
             
-            WindowEvents->WindowStateChanged(windowState);
+            if (windowState != _lastWindowState)
+            {
+                _lastWindowState = windowState;
+                
+                WindowEvents->WindowStateChanged(windowState);
+            }
         }
     }
     
+protected:
     virtual NSWindowStyleMask GetStyle() override
     {
         unsigned long s = NSWindowStyleMaskBorderless;
@@ -1312,6 +1324,11 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     }
 }
 
+- (void)windowDidResize:(NSNotification *)notification
+{
+    _parent->OnResized();
+}
+
 - (BOOL)windowShouldZoom:(NSWindow *)window toFrame:(NSRect)newFrame
 {
     return true;
@@ -1382,6 +1399,7 @@ protected:
             [Window setContentSize:NSSize{x, y}];
             
             [Window setFrameTopLeftPoint:ToNSPoint(ConvertPointY(lastPositionSet))];
+            
             return S_OK;
         }
     }
diff --git a/nukebuild/Build.cs b/nukebuild/Build.cs
index 7b3b8465ce..358846a14e 100644
--- a/nukebuild/Build.cs
+++ b/nukebuild/Build.cs
@@ -13,6 +13,7 @@ using Nuke.Common.Tooling;
 using Nuke.Common.Tools.DotNet;
 using Nuke.Common.Tools.MSBuild;
 using Nuke.Common.Utilities;
+using Nuke.Common.Utilities.Collections;
 using static Nuke.Common.EnvironmentInfo;
 using static Nuke.Common.IO.FileSystemTasks;
 using static Nuke.Common.IO.PathConstruction;
@@ -26,11 +27,13 @@ using static Nuke.Common.Tools.VSWhere.VSWhereTasks;
  running and debugging a particular target (optionally without deps) would be way easier
  ReSharper/Rider - https://plugins.jetbrains.com/plugin/10803-nuke-support
  VSCode - https://marketplace.visualstudio.com/items?itemName=nuke.support
- 
+
  */
 
 partial class Build : NukeBuild
 {
+    [Solution("Avalonia.sln")] readonly Solution Solution;
+
     static Lazy<string> MsBuildExe = new Lazy<string>(() =>
     {
         if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -54,7 +57,7 @@ partial class Build : NukeBuild
     protected override void OnBuildInitialized()
     {
         Parameters = new BuildParameters(this);
-        Information("Building version {0} of Avalonia ({1}) using version {2} of Nuke.", 
+        Information("Building version {0} of Avalonia ({1}) using version {2} of Nuke.",
             Parameters.Version,
             Parameters.Configuration,
             typeof(NukeBuild).Assembly.GetName().Version.ToString());
@@ -93,29 +96,24 @@ partial class Build : NukeBuild
         string projectFile,
         Configure<MSBuildSettings> configurator = null)
     {
-        return MSBuild(projectFile, c =>
-        {
+        return MSBuild(c => c
+            .SetProjectFile(projectFile)
             // This is required for VS2019 image on Azure Pipelines
-            if (Parameters.IsRunningOnWindows && Parameters.IsRunningOnAzure)
-            {
-                var javaSdk = Environment.GetEnvironmentVariable("JAVA_HOME_8_X64");
-                if (javaSdk != null)
-                    c = c.AddProperty("JavaSdkDirectory", javaSdk);
-            }
-
-            c = c.AddProperty("PackageVersion", Parameters.Version)
-                .AddProperty("iOSRoslynPathHackRequired", "true")
-                .SetToolPath(MsBuildExe.Value)
-                .SetConfiguration(Parameters.Configuration)
-                .SetVerbosity(MSBuildVerbosity.Minimal);
-            c = configurator?.Invoke(c) ?? c;
-            return c;
-        });
+            .When(Parameters.IsRunningOnWindows &&
+                  Parameters.IsRunningOnAzure, c => c
+                .AddProperty("JavaSdkDirectory", GetVariable<string>("JAVA_HOME_8_X64")))
+            .AddProperty("PackageVersion", Parameters.Version)
+            .AddProperty("iOSRoslynPathHackRequired", true)
+            .SetToolPath(MsBuildExe.Value)
+            .SetConfiguration(Parameters.Configuration)
+            .SetVerbosity(MSBuildVerbosity.Minimal)
+            .Apply(configurator));
     }
+
     Target Clean => _ => _.Executes(() =>
     {
-        DeleteDirectories(Parameters.BuildDirs);
-        EnsureCleanDirectories(Parameters.BuildDirs);
+        Parameters.BuildDirs.ForEach(DeleteDirectory);
+        Parameters.BuildDirs.ForEach(EnsureCleanDirectory);
         EnsureCleanDirectory(Parameters.ArtifactsDir);
         EnsureCleanDirectory(Parameters.NugetIntermediateRoot);
         EnsureCleanDirectory(Parameters.NugetRoot);
@@ -134,97 +132,84 @@ partial class Build : NukeBuild
                 );
 
             else
-                DotNetBuild(Parameters.MSBuildSolution, c => c
+                DotNetBuild(c => c
+                    .SetProjectFile(Parameters.MSBuildSolution)
                     .AddProperty("PackageVersion", Parameters.Version)
                     .SetConfiguration(Parameters.Configuration)
                 );
         });
-    
-    void RunCoreTest(string project)
+
+    void RunCoreTest(string projectName)
     {
-        if(!project.EndsWith(".csproj"))
-            project = System.IO.Path.Combine(project, System.IO.Path.GetFileName(project)+".csproj");
-        Information("Running tests from " + project);
-        XDocument xdoc;
-        using (var s = File.OpenRead(project))
-            xdoc = XDocument.Load(s);
-
-        List<string> frameworks = null;
-        var targets = xdoc.Root.Descendants("TargetFrameworks").FirstOrDefault();
-        if (targets != null)
-            frameworks = targets.Value.Split(';').Where(f => !string.IsNullOrWhiteSpace(f)).ToList();
-        else 
-            frameworks = new List<string> {xdoc.Root.Descendants("TargetFramework").First().Value};
-        
-        foreach(var fw in frameworks)
+        Information($"Running tests from {projectName}");
+        var project = Solution.GetProject(projectName).NotNull("project != null");
+
+        foreach (var fw in project.GetTargetFrameworks())
         {
             if (fw.StartsWith("net4")
-                && RuntimeInformation.IsOSPlatform(OSPlatform.Linux) 
+                && RuntimeInformation.IsOSPlatform(OSPlatform.Linux)
                 && Environment.GetEnvironmentVariable("FORCE_LINUX_TESTS") != "1")
             {
-                Information($"Skipping {fw} tests on Linux - https://github.com/mono/mono/issues/13969");
+                Information($"Skipping {projectName} ({fw}) tests on Linux - https://github.com/mono/mono/issues/13969");
                 continue;
             }
 
-            Information("Running for " + fw);
-            DotNetTest(c =>
-            {
-                c = c
-                    .SetProjectFile(project)
-                    .SetConfiguration(Parameters.Configuration)
-                    .SetFramework(fw)
-                    .EnableNoBuild()
-                    .EnableNoRestore();
-                // NOTE: I can see that we could maybe add another extension method "Switch" or "If" to make this more  convenient
-                if (Parameters.PublishTestResults)
-                    c = c.SetLogger("trx").SetResultsDirectory(Parameters.TestResultsRoot);
-                return c;
-            });
+            Information($"Running for {projectName} ({fw}) ...");
+
+            DotNetTest(c => c
+                .SetProjectFile(project)
+                .SetConfiguration(Parameters.Configuration)
+                .SetFramework(fw)
+                .EnableNoBuild()
+                .EnableNoRestore()
+                .When(Parameters.PublishTestResults, c => c
+                    .SetLogger("trx")
+                    .SetResultsDirectory(Parameters.TestResultsRoot)));
         }
     }
 
     Target RunCoreLibsTests => _ => _
-        .OnlyWhen(() => !Parameters.SkipTests)
+        .OnlyWhenStatic(() => !Parameters.SkipTests)
         .DependsOn(Compile)
         .Executes(() =>
         {
-            RunCoreTest("./tests/Avalonia.Animation.UnitTests");
-            RunCoreTest("./tests/Avalonia.Base.UnitTests");
-            RunCoreTest("./tests/Avalonia.Controls.UnitTests");
-            RunCoreTest("./tests/Avalonia.Controls.DataGrid.UnitTests");
-            RunCoreTest("./tests/Avalonia.Input.UnitTests");
-            RunCoreTest("./tests/Avalonia.Interactivity.UnitTests");
-            RunCoreTest("./tests/Avalonia.Layout.UnitTests");
-            RunCoreTest("./tests/Avalonia.Markup.UnitTests");
-            RunCoreTest("./tests/Avalonia.Markup.Xaml.UnitTests");
-            RunCoreTest("./tests/Avalonia.Styling.UnitTests");
-            RunCoreTest("./tests/Avalonia.Visuals.UnitTests");
-            RunCoreTest("./tests/Avalonia.Skia.UnitTests");
-            RunCoreTest("./tests/Avalonia.ReactiveUI.UnitTests");
+            RunCoreTest("Avalonia.Animation.UnitTests");
+            RunCoreTest("Avalonia.Base.UnitTests");
+            RunCoreTest("Avalonia.Controls.UnitTests");
+            RunCoreTest("Avalonia.Controls.DataGrid.UnitTests");
+            RunCoreTest("Avalonia.Input.UnitTests");
+            RunCoreTest("Avalonia.Interactivity.UnitTests");
+            RunCoreTest("Avalonia.Layout.UnitTests");
+            RunCoreTest("Avalonia.Markup.UnitTests");
+            RunCoreTest("Avalonia.Markup.Xaml.UnitTests");
+            RunCoreTest("Avalonia.Styling.UnitTests");
+            RunCoreTest("Avalonia.Visuals.UnitTests");
+            RunCoreTest("Avalonia.Skia.UnitTests");
+            RunCoreTest("Avalonia.ReactiveUI.UnitTests");
         });
 
     Target RunRenderTests => _ => _
-        .OnlyWhen(() => !Parameters.SkipTests)
+        .OnlyWhenStatic(() => !Parameters.SkipTests)
         .DependsOn(Compile)
         .Executes(() =>
         {
-            RunCoreTest("./tests/Avalonia.Skia.RenderTests/Avalonia.Skia.RenderTests.csproj");
+            RunCoreTest("Avalonia.Skia.RenderTests");
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
-                RunCoreTest("./tests/Avalonia.Direct2D1.RenderTests/Avalonia.Direct2D1.RenderTests.csproj");
+                RunCoreTest("Avalonia.Direct2D1.RenderTests");
         });
-    
+
     Target RunDesignerTests => _ => _
-        .OnlyWhen(() => !Parameters.SkipTests && Parameters.IsRunningOnWindows)
+        .OnlyWhenStatic(() => !Parameters.SkipTests && Parameters.IsRunningOnWindows)
         .DependsOn(Compile)
         .Executes(() =>
         {
-            RunCoreTest("./tests/Avalonia.DesignerSupport.Tests");
+            RunCoreTest("Avalonia.DesignerSupport.Tests");
         });
 
     [PackageExecutable("JetBrains.dotMemoryUnit", "dotMemoryUnit.exe")] readonly Tool DotMemoryUnit;
 
     Target RunLeakTests => _ => _
-        .OnlyWhen(() => !Parameters.SkipTests && Parameters.IsRunningOnWindows)
+        .OnlyWhenStatic(() => !Parameters.SkipTests && Parameters.IsRunningOnWindows)
         .DependsOn(Compile)
         .Executes(() =>
         {
@@ -235,7 +220,7 @@ partial class Build : NukeBuild
         });
 
     Target ZipFiles => _ => _
-        .After(CreateNugetPackages, Compile, RunCoreLibsTests, Package)    
+        .After(CreateNugetPackages, Compile, RunCoreLibsTests, Package)
         .Executes(() =>
         {
             var data = Parameters;
@@ -259,9 +244,10 @@ partial class Build : NukeBuild
                 MsBuildCommon(Parameters.MSBuildSolution, c => c
                     .AddTargets("Pack"));
             else
-                DotNetPack(Parameters.MSBuildSolution, c =>
-                    c.SetConfiguration(Parameters.Configuration)
-                        .AddProperty("PackageVersion", Parameters.Version));
+                DotNetPack(c => c
+                    .SetProject(Parameters.MSBuildSolution)
+                    .SetConfiguration(Parameters.Configuration)
+                    .AddProperty("PackageVersion", Parameters.Version));
         });
 
     Target CreateNugetPackages => _ => _
@@ -274,32 +260,40 @@ partial class Build : NukeBuild
                 new NumergeNukeLogger()))
                 throw new Exception("Package merge failed");
         });
-    
+
     Target RunTests => _ => _
         .DependsOn(RunCoreLibsTests)
         .DependsOn(RunRenderTests)
         .DependsOn(RunDesignerTests)
         .DependsOn(RunLeakTests);
-    
+
     Target Package => _ => _
         .DependsOn(RunTests)
         .DependsOn(CreateNugetPackages);
-    
+
     Target CiAzureLinux => _ => _
         .DependsOn(RunTests);
-    
+
     Target CiAzureOSX => _ => _
         .DependsOn(Package)
         .DependsOn(ZipFiles);
-    
+
     Target CiAzureWindows => _ => _
         .DependsOn(Package)
         .DependsOn(ZipFiles);
 
-    
+
     public static int Main() =>
         RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
             ? Execute<Build>(x => x.Package)
             : Execute<Build>(x => x.RunTests);
 
 }
+
+public static class ToolSettingsExtensions
+{
+    public static T Apply<T>(this T settings, Configure<T> configurator)
+    {
+        return configurator != null ? configurator(settings) : settings;
+    }
+}
diff --git a/nukebuild/BuildParameters.cs b/nukebuild/BuildParameters.cs
index 65ba5e9756..149716b416 100644
--- a/nukebuild/BuildParameters.cs
+++ b/nukebuild/BuildParameters.cs
@@ -4,24 +4,21 @@ using System.Linq;
 using System.Runtime.InteropServices;
 using System.Xml.Linq;
 using Nuke.Common;
-using Nuke.Common.BuildServers;
-using Nuke.Common.Execution;
+using Nuke.Common.CI.AzurePipelines;
 using Nuke.Common.IO;
-using static Nuke.Common.IO.FileSystemTasks;
 using static Nuke.Common.IO.PathConstruction;
-using static Nuke.Common.Tools.MSBuild.MSBuildTasks;
 
 public partial class Build
 {
     [Parameter("configuration")]
     public string Configuration { get; set; }
-    
+
     [Parameter("skip-tests")]
     public bool SkipTests { get; set; }
-    
+
     [Parameter("force-nuget-version")]
     public string ForceNugetVersion { get; set; }
-    
+
     public class BuildParameters
     {
         public string Configuration { get; }
@@ -79,15 +76,15 @@ public partial class Build
             IsRunningOnUnix = Environment.OSVersion.Platform == PlatformID.Unix ||
                               Environment.OSVersion.Platform == PlatformID.MacOSX;
             IsRunningOnWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
-            IsRunningOnAzure = Host == HostType.TeamServices ||
+            IsRunningOnAzure = Host == HostType.AzurePipelines ||
                                Environment.GetEnvironmentVariable("LOGNAME") == "vsts";
 
             if (IsRunningOnAzure)
             {
-                RepositoryName = TeamServices.Instance.RepositoryUri;
-                RepositoryBranch = TeamServices.Instance.SourceBranch;
-                IsPullRequest = TeamServices.Instance.PullRequestId.HasValue;
-                IsMainRepo = StringComparer.OrdinalIgnoreCase.Equals(MainRepo, TeamServices.Instance.RepositoryUri);
+                RepositoryName = AzurePipelines.Instance.RepositoryUri;
+                RepositoryBranch = AzurePipelines.Instance.SourceBranch;
+                IsPullRequest = AzurePipelines.Instance.PullRequestId.HasValue;
+                IsMainRepo = StringComparer.OrdinalIgnoreCase.Equals(MainRepo, AzurePipelines.Instance.RepositoryUri);
             }
             IsMainRepo =
                 StringComparer.OrdinalIgnoreCase.Equals(MainRepo,
diff --git a/nukebuild/Shims.cs b/nukebuild/Shims.cs
index 461d617643..1ac14bf622 100644
--- a/nukebuild/Shims.cs
+++ b/nukebuild/Shims.cs
@@ -19,9 +19,9 @@ public partial class Build
         Logger.Info(info, args);
     }
 
-    private void Zip(PathConstruction.AbsolutePath target, params string[] paths) => Zip(target, paths.AsEnumerable());
+    private void Zip(AbsolutePath target, params string[] paths) => Zip(target, paths.AsEnumerable());
 
-    private void Zip(PathConstruction.AbsolutePath target, IEnumerable<string> paths)
+    private void Zip(AbsolutePath target, IEnumerable<string> paths)
     {
         var targetPath = target.ToString();
         bool finished = false, atLeastOneFileAdded = false;
@@ -38,7 +38,7 @@ public partial class Build
                         fileStream.CopyTo(entryStream);
                     atLeastOneFileAdded = true;
                 }
-                
+
                 foreach (var path in paths)
                 {
                     if (Directory.Exists(path))
@@ -64,7 +64,7 @@ public partial class Build
 
             finished = true;
         }
-        finally 
+        finally
         {
             try
             {
diff --git a/nukebuild/_build.csproj b/nukebuild/_build.csproj
index 2a736e4653..584c36d033 100644
--- a/nukebuild/_build.csproj
+++ b/nukebuild/_build.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
     <RootNamespace></RootNamespace>
     <IsPackable>False</IsPackable>
@@ -10,7 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Nuke.Common" Version="0.12.3" />
+    <PackageReference Include="Nuke.Common" Version="0.24.0" />
     <PackageReference Include="xunit.runner.console" Version="2.3.1" />
     <PackageReference Include="JetBrains.dotMemoryUnit" Version="3.0.20171219.105559" />
     <PackageReference Include="vswhere" Version="2.6.7" Condition=" '$(OS)' == 'Windows_NT' " />
@@ -20,11 +20,11 @@
     <NukeMetadata Include="**\*.json" Exclude="bin\**;obj\**" />
     <NukeExternalFiles Include="**\*.*.ext" Exclude="bin\**;obj\**" />
     <None Remove="*.csproj.DotSettings;*.ref.*.txt" />
-    
+
     <!-- Common build related files -->
     <None Include="..\build.ps1" />
     <None Include="..\build.sh" />
-    <None Include="..\.nuke" />     
+    <None Include="..\.nuke" />
     <None Include="..\global.json" Condition="Exists('..\global.json')" />
     <None Include="..\nuget.config" Condition="Exists('..\nuget.config')" />
     <None Include="..\Jenkinsfile" Condition="Exists('..\Jenkinsfile')" />
diff --git a/samples/BindingDemo/BindingDemo.csproj b/samples/BindingDemo/BindingDemo.csproj
index 3005fdbc51..267ee21fbc 100644
--- a/samples/BindingDemo/BindingDemo.csproj
+++ b/samples/BindingDemo/BindingDemo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>netcoreapp2.0;net461</TargetFrameworks>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />
diff --git a/samples/ControlCatalog.NetCore/ControlCatalog.NetCore.csproj b/samples/ControlCatalog.NetCore/ControlCatalog.NetCore.csproj
index 7919c3ac5a..772af9eacd 100644
--- a/samples/ControlCatalog.NetCore/ControlCatalog.NetCore.csproj
+++ b/samples/ControlCatalog.NetCore/ControlCatalog.NetCore.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
   </PropertyGroup>
 
diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml b/samples/ControlCatalog/Pages/DialogsPage.xaml
index 60f8e3656e..98ca2887d8 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml
@@ -6,6 +6,7 @@
       <Button Name="OpenFile">Open File</Button>
       <Button Name="SaveFile">Save File</Button>
       <Button Name="SelectFolder">Select Folder</Button>
+      <Button Name="OpenBoth">Select Both</Button>
       <Button Name="DecoratedWindow">Decorated window</Button>
       <Button Name="DecoratedWindowDialog">Decorated window (dialog)</Button>
       <Button Name="Dialog">Dialog</Button>
diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index d207689223..127fa4d1df 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -1,5 +1,9 @@
+using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
 using Avalonia.Controls;
+using Avalonia.Dialogs;
 using Avalonia.Markup.Xaml;
 #pragma warning disable 4014
 
@@ -34,7 +38,9 @@ namespace ControlCatalog.Pages
                 new OpenFileDialog()
                 {
                     Title = "Open file",
-                    Filters = GetFilters()
+                    Filters = GetFilters(),
+                    // Almost guaranteed to exist
+                    InitialFileName = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName
                 }.ShowAsync(GetWindow());
             };
             this.FindControl<Button>("SaveFile").Click += delegate
@@ -42,16 +48,30 @@ namespace ControlCatalog.Pages
                 new SaveFileDialog()
                 {
                     Title = "Save file",
-                    Filters = GetFilters()
+                    Filters = GetFilters(),
+                    InitialFileName = "test.txt"
                 }.ShowAsync(GetWindow());
             };
             this.FindControl<Button>("SelectFolder").Click += delegate
             {
                 new OpenFolderDialog()
                 {
-                    Title = "Select folder"
+                    Title = "Select folder",
                 }.ShowAsync(GetWindow());
             };
+            this.FindControl<Button>("OpenBoth").Click += async delegate
+            {
+                var res = await new OpenFileDialog()
+                {
+                    Title = "Select both",
+                    AllowMultiple = true
+                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
+                {
+                    AllowDirectorySelection = true
+                });
+                if (res != null)
+                    Console.WriteLine("Selected: \n" + string.Join("\n", res));
+            };
             this.FindControl<Button>("DecoratedWindow").Click += delegate
             {
                 new DecoratedWindow().Show();
diff --git a/samples/PlatformSanityChecks/PlatformSanityChecks.csproj b/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
index 2adef5f64e..86d762a5bc 100644
--- a/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
+++ b/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/samples/Previewer/Previewer.csproj b/samples/Previewer/Previewer.csproj
index 2cdde0c945..cd3daf61e1 100644
--- a/samples/Previewer/Previewer.csproj
+++ b/samples/Previewer/Previewer.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <Compile Update="**\*.xaml.cs">
diff --git a/samples/RemoteDemo/RemoteDemo.csproj b/samples/RemoteDemo/RemoteDemo.csproj
index 2d7699561a..530cad805f 100644
--- a/samples/RemoteDemo/RemoteDemo.csproj
+++ b/samples/RemoteDemo/RemoteDemo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\ControlCatalog\ControlCatalog.csproj" />
diff --git a/samples/RenderDemo/RenderDemo.csproj b/samples/RenderDemo/RenderDemo.csproj
index 3005fdbc51..267ee21fbc 100644
--- a/samples/RenderDemo/RenderDemo.csproj
+++ b/samples/RenderDemo/RenderDemo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>netcoreapp2.0;net461</TargetFrameworks>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />
diff --git a/samples/VirtualizationDemo/VirtualizationDemo.csproj b/samples/VirtualizationDemo/VirtualizationDemo.csproj
index 3005fdbc51..267ee21fbc 100644
--- a/samples/VirtualizationDemo/VirtualizationDemo.csproj
+++ b/samples/VirtualizationDemo/VirtualizationDemo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>netcoreapp2.0;net461</TargetFrameworks>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />
diff --git a/scripts/ReplaceNugetCache.ps1 b/scripts/ReplaceNugetCache.ps1
index 70f5eaa40b..52743a95eb 100644
--- a/scripts/ReplaceNugetCache.ps1
+++ b/scripts/ReplaceNugetCache.ps1
@@ -1,5 +1,5 @@
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netcoreapp2.0\
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netstandard2.0\
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Win32.dll ~\.nuget\packages\avalonia.win32\$args\lib\netstandard2.0\
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Skia.dll ~\.nuget\packages\avalonia.skia\$args\lib\netstandard2.0\
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Skia.dll ~\.nuget\packages\avalonia.direct2d1\$args\lib\netstandard2.0\
+copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp3.1\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netcoreapp3.1\
+copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp3.1\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netstandard2.0\
+copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp3.1\Avalonia.Win32.dll ~\.nuget\packages\avalonia.win32\$args\lib\netstandard2.0\
+copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp3.1\Avalonia.Skia.dll ~\.nuget\packages\avalonia.skia\$args\lib\netstandard2.0\
+copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp3.1\Avalonia.Skia.dll ~\.nuget\packages\avalonia.direct2d1\$args\lib\netstandard2.0\
diff --git a/scripts/ReplaceNugetCache.sh b/scripts/ReplaceNugetCache.sh
index e1c0487d60..7ac601571d 100755
--- a/scripts/ReplaceNugetCache.sh
+++ b/scripts/ReplaceNugetCache.sh
@@ -1,8 +1,8 @@
  #!/usr/bin/env bash
  
- cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp2.0/Avalonia**.dll ~/.nuget/packages/avalonia/$1/lib/netcoreapp2.0/
- cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp2.0/Avalonia**.dll ~/.nuget/packages/avalonia/$1/lib/netstandard2.0/
- cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp2.0/Avalonia**.dll ~/.nuget/packages/avalonia.skia/$1/lib/netstandard2.0/
- cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp2.0/Avalonia**.dll ~/.nuget/packages/avalonia.native/$1/lib/netstandard2.0/
+ cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp3.1/Avalonia**.dll ~/.nuget/packages/avalonia/$1/lib/netcoreapp3.1/
+ cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp3.1/Avalonia**.dll ~/.nuget/packages/avalonia/$1/lib/netstandard2.0/
+ cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp3.1/Avalonia**.dll ~/.nuget/packages/avalonia.skia/$1/lib/netstandard2.0/
+ cp ../samples/ControlCatalog.NetCore/bin/Debug/netcoreapp3.1/Avalonia**.dll ~/.nuget/packages/avalonia.native/$1/lib/netstandard2.0/
  
  
diff --git a/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs b/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
index 6e1c4cb0e3..887641b5c3 100644
--- a/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
+++ b/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
@@ -30,7 +30,23 @@ namespace Avalonia.Data.Converters
         /// <inheritdoc/>
         public object Convert(IList<object> values, Type targetType, object parameter, CultureInfo culture)
         {
-            var converted = values.OfType<TIn>().ToList();
+            //standard OfType skip null values, even they are valid for the Type
+            static IEnumerable<TIn> OfTypeWithDefaultSupport(IList<object> list)
+            {
+                foreach (object obj in list)
+                {
+                    if (obj is TIn result)
+                    {
+                        yield return result;
+                    }
+                    else if (Equals(obj, default(TIn)))
+                    {
+                        yield return default(TIn);
+                    }
+                }
+            }
+
+            var converted = OfTypeWithDefaultSupport(values).ToList();
 
             if (converted.Count == values.Count)
             {
diff --git a/src/Avalonia.Base/EnumExtensions.cs b/src/Avalonia.Base/EnumExtensions.cs
new file mode 100644
index 0000000000..d847ab2faa
--- /dev/null
+++ b/src/Avalonia.Base/EnumExtensions.cs
@@ -0,0 +1,20 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Avalonia
+{
+    /// <summary>
+    /// Provides extension methods for enums.
+    /// </summary>
+    public static class EnumExtensions
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool HasFlagCustom<T>(this T value, T flag) where T : unmanaged, Enum
+        {
+            var intValue = *(int*)&value;
+            var intFlag = *(int*)&flag;
+
+            return (intValue & intFlag) == intFlag;
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Utilities/TypeUtilities.cs b/src/Avalonia.Base/Utilities/TypeUtilities.cs
index d85eb4cd76..39736ab389 100644
--- a/src/Avalonia.Base/Utilities/TypeUtilities.cs
+++ b/src/Avalonia.Base/Utilities/TypeUtilities.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.ComponentModel;
 using System.Globalization;
 using System.Linq;
 using System.Reflection;
@@ -188,6 +189,14 @@ namespace Avalonia.Utilities
                 }
             }
 
+            var typeConverter = TypeDescriptor.GetConverter(to);
+
+            if (typeConverter.CanConvertFrom(from) == true)
+            {
+                result = typeConverter.ConvertFrom(null, culture, value);
+                return true;
+            }
+
             var cast = FindTypeConversionOperatorMethod(from, to, OperatorType.Implicit | OperatorType.Explicit);
 
             if (cast != null)
diff --git a/src/Avalonia.Base/Utilities/WeakEventHandlerManager.cs b/src/Avalonia.Base/Utilities/WeakEventHandlerManager.cs
index 37e25d0fac..aca08f5259 100644
--- a/src/Avalonia.Base/Utilities/WeakEventHandlerManager.cs
+++ b/src/Avalonia.Base/Utilities/WeakEventHandlerManager.cs
@@ -183,11 +183,16 @@ namespace Avalonia.Utilities
                 for (int c = 0; c < _count; c++)
                 {
                     var r = _data[c];
+
+                    TSubscriber target = null;
+
+                    r.Subscriber?.TryGetTarget(out target);
+
                     //Mark current index as first empty
-                    if (r.Subscriber == null && empty == -1)
+                    if (target == null && empty == -1)
                         empty = c;
                     //If current element isn't null and we have an empty one
-                    if (r.Subscriber != null && empty != -1)
+                    if (target != null && empty != -1)
                     {
                         _data[c] = default;
                         _data[empty] = r;
diff --git a/src/Avalonia.Controls/ContextMenu.cs b/src/Avalonia.Controls/ContextMenu.cs
index 5dfa5863f5..a770d860cb 100644
--- a/src/Avalonia.Controls/ContextMenu.cs
+++ b/src/Avalonia.Controls/ContextMenu.cs
@@ -20,6 +20,8 @@ namespace Avalonia.Controls
         private static readonly ITemplate<IPanel> DefaultPanel =
             new FuncTemplate<IPanel>(() => new StackPanel { Orientation = Orientation.Vertical });
         private Popup _popup;
+        private Control _attachedControl;
+        private IInputElement _previousFocus;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ContextMenu"/> class.
@@ -69,13 +71,16 @@ namespace Avalonia.Controls
         {
             var control = (Control)e.Sender;
 
-            if (e.OldValue != null)
+            if (e.OldValue is ContextMenu oldMenu)
             {
                 control.PointerReleased -= ControlPointerReleased;
+                oldMenu._attachedControl = null;
+                ((ISetLogicalParent)oldMenu._popup)?.SetParent(null);
             }
 
-            if (e.NewValue != null)
+            if (e.NewValue is ContextMenu newMenu)
             {
+                newMenu._attachedControl = control;
                 control.PointerReleased += ControlPointerReleased;
             }
         }
@@ -91,8 +96,18 @@ namespace Avalonia.Controls
         /// <param name="control">The control.</param>
         public void Open(Control control)
         {
-            if (control == null)
+            if (control is null && _attachedControl is null)
+            {
                 throw new ArgumentNullException(nameof(control));
+            }
+
+            if (control is object && _attachedControl is object && control != _attachedControl)
+            {
+                throw new ArgumentException(
+                    "Cannot show ContentMenu on a different control to the one it is attached to.",
+                    nameof(control));
+            }
+
             if (IsOpen)
             {
                 return;
@@ -146,36 +161,38 @@ namespace Avalonia.Controls
             return new MenuItemContainerGenerator(this);
         }
 
-        private void CloseCore()
-        {
-            SelectedIndex = -1;
-            IsOpen = false;
-
-            RaiseEvent(new RoutedEventArgs
-            {
-                RoutedEvent = MenuClosedEvent,
-                Source = this,
-            });
-        }
-
         private void PopupOpened(object sender, EventArgs e)
         {
+            _previousFocus = FocusManager.Instance?.Current;
             Focus();
         }
 
         private void PopupClosed(object sender, EventArgs e)
         {
-            var contextMenu = (sender as Popup)?.Child as ContextMenu;
-
-            if (contextMenu != null)
+            foreach (var i in LogicalChildren)
             {
-                foreach (var i in contextMenu.GetLogicalChildren().OfType<MenuItem>())
+                if (i is MenuItem menuItem)
                 {
-                    i.IsSubMenuOpen = false;
+                    menuItem.IsSubMenuOpen = false;
                 }
+            }
 
-                contextMenu.CloseCore();
+            SelectedIndex = -1;
+            IsOpen = false;
+
+            if (_attachedControl is null)
+            {
+                ((ISetLogicalParent)_popup).SetParent(null);
             }
+
+            // HACK: Reset the focus when the popup is closed. We need to fix this so it's automatic.
+            FocusManager.Instance?.Focus(_previousFocus);
+
+            RaiseEvent(new RoutedEventArgs
+            {
+                RoutedEvent = MenuClosedEvent,
+                Source = this,
+            });
         }
 
         private static void ControlPointerReleased(object sender, PointerReleasedEventArgs e)
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index bf22f0a08a..5f7a36f2f9 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -504,7 +504,10 @@ namespace Avalonia.Controls
                 result = container.GetControl(direction, c, wrap);
                 from = from ?? result;
 
-                if (result?.Focusable == true)
+                if (result != null &&
+                    result.Focusable &&
+                    result.IsEffectivelyEnabled &&
+                    result.IsEffectivelyVisible)
                 {
                     return result;
                 }
diff --git a/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs b/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
index 90969fef56..566351c280 100644
--- a/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
+++ b/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
@@ -101,7 +101,7 @@ namespace Avalonia.Controls.Platform
             if (_root is TopLevel tl && tl.PlatformImpl is IEmbeddableWindowImpl eimpl)
                 eimpl.LostFocus -= TopLevelLostPlatformFocus;
 
-            _inputManagerSubscription.Dispose();
+            _inputManagerSubscription?.Dispose();
 
             Menu = null;
             _root = null;
diff --git a/src/Avalonia.Controls/Primitives/PopupRoot.cs b/src/Avalonia.Controls/Primitives/PopupRoot.cs
index 74a6d288f4..c912cbaa3b 100644
--- a/src/Avalonia.Controls/Primitives/PopupRoot.cs
+++ b/src/Avalonia.Controls/Primitives/PopupRoot.cs
@@ -118,20 +118,41 @@ namespace Avalonia.Controls.Primitives
             });
         }
 
-        /// <summary>
-        /// Carries out the arrange pass of the window.
-        /// </summary>
-        /// <param name="finalSize">The final window size.</param>
-        /// <returns>The <paramref name="finalSize"/> parameter unchanged.</returns>
-        protected override Size ArrangeOverride(Size finalSize)
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            var measured = base.MeasureOverride(availableSize);
+            var width = measured.Width;
+            var height = measured.Height;
+            var widthCache = Width;
+            var heightCache = Height;
+
+            if (!double.IsNaN(widthCache))
+            {
+                width = widthCache;
+            }
+
+            width = Math.Min(width, MaxWidth);
+            width = Math.Max(width, MinWidth);
+
+            if (!double.IsNaN(heightCache))
+            {
+                height = heightCache;
+            }
+
+            height = Math.Min(height, MaxHeight);
+            height = Math.Max(height, MinHeight);
+
+            return new Size(width, height);
+        }
+
+        protected override sealed Size ArrangeSetBounds(Size size)
         {
             using (BeginAutoSizing())
             {
-                _positionerParameters.Size = finalSize;
+                _positionerParameters.Size = size;
                 UpdatePosition();
+                return ClientSize;
             }
-
-            return base.ArrangeOverride(PlatformImpl?.ClientSize ?? default(Size));
         }
     }
 }
diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index f66a248aaf..439f5442b7 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -129,7 +129,7 @@ namespace Avalonia.Controls
 
             ShowInTaskbarProperty.Changed.AddClassHandler<Window>((w, e) => w.PlatformImpl?.ShowTaskbarIcon((bool)e.NewValue));
 
-            IconProperty.Changed.AddClassHandler<Window>((s, e) => s.PlatformImpl?.SetIcon(((WindowIcon)e.NewValue).PlatformImpl));
+            IconProperty.Changed.AddClassHandler<Window>((s, e) => s.PlatformImpl?.SetIcon(((WindowIcon)e.NewValue)?.PlatformImpl));
 
             CanResizeProperty.Changed.AddClassHandler<Window>((w, e) => w.PlatformImpl?.CanResize((bool)e.NewValue));
 
@@ -268,22 +268,7 @@ namespace Avalonia.Controls
         /// Should be called from left mouse button press event handler
         /// </summary>
         public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e) => PlatformImpl?.BeginResizeDrag(edge, e);
-        
-        /// <summary>
-        /// Carries out the arrange pass of the window.
-        /// </summary>
-        /// <param name="finalSize">The final window size.</param>
-        /// <returns>The <paramref name="finalSize"/> parameter unchanged.</returns>
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            using (BeginAutoSizing())
-            {
-                PlatformImpl?.Resize(finalSize);
-            }
 
-            return base.ArrangeOverride(PlatformImpl?.ClientSize ?? default(Size));
-        }
-        
         /// <inheritdoc/>
         Size ILayoutRoot.MaxClientSize => _maxPlatformClientSize;
 
@@ -405,6 +390,19 @@ namespace Avalonia.Controls
 
             EnsureInitialized();
             IsVisible = true;
+
+            var initialSize = new Size(
+                double.IsNaN(Width) ? ClientSize.Width : Width,
+                double.IsNaN(Height) ? ClientSize.Height : Height);
+
+            if (initialSize != ClientSize)
+            {
+                using (BeginAutoSizing())
+                {
+                    PlatformImpl?.Resize(initialSize);
+                }
+            }
+
             LayoutManager.ExecuteInitialLayoutPass(this);
 
             using (BeginAutoSizing())
@@ -524,38 +522,60 @@ namespace Avalonia.Controls
             }
         }
 
-        /// <inheritdoc/>
         protected override Size MeasureOverride(Size availableSize)
         {
             var sizeToContent = SizeToContent;
             var clientSize = ClientSize;
-            Size constraint = clientSize;
+            var constraint = clientSize;
 
-            if ((sizeToContent & SizeToContent.Width) != 0)
+            if (sizeToContent.HasFlagCustom(SizeToContent.Width))
             {
                 constraint = constraint.WithWidth(double.PositiveInfinity);
             }
 
-            if ((sizeToContent & SizeToContent.Height) != 0)
+            if (sizeToContent.HasFlagCustom(SizeToContent.Height))
             {
                 constraint = constraint.WithHeight(double.PositiveInfinity);
             }
 
             var result = base.MeasureOverride(constraint);
 
-            if ((sizeToContent & SizeToContent.Width) == 0)
+            if (!sizeToContent.HasFlagCustom(SizeToContent.Width))
             {
-                result = result.WithWidth(clientSize.Width);
+                if (!double.IsInfinity(availableSize.Width))
+                {
+                    result = result.WithWidth(availableSize.Width);
+                }
+                else
+                {
+                    result = result.WithWidth(clientSize.Width);
+                }
             }
 
-            if ((sizeToContent & SizeToContent.Height) == 0)
+            if (!sizeToContent.HasFlagCustom(SizeToContent.Height))
             {
-                result = result.WithHeight(clientSize.Height);
+                if (!double.IsInfinity(availableSize.Height))
+                {
+                    result = result.WithHeight(availableSize.Height);
+                }
+                else
+                {
+                    result = result.WithHeight(clientSize.Height);
+                }
             }
 
             return result;
         }
 
+        protected sealed override Size ArrangeSetBounds(Size size)
+        {
+            using (BeginAutoSizing())
+            {
+                PlatformImpl?.Resize(size);
+                return ClientSize;
+            }
+        }
+
         protected sealed override void HandleClosed()
         {
             RaiseEvent(new RoutedEventArgs(WindowClosedEvent));
@@ -571,6 +591,9 @@ namespace Avalonia.Controls
                 SizeToContent = SizeToContent.Manual;
             }
 
+            Width = clientSize.Width;
+            Height = clientSize.Height;
+
             base.HandleResized(clientSize);
         }
 
diff --git a/src/Avalonia.Controls/WindowBase.cs b/src/Avalonia.Controls/WindowBase.cs
index 196110edf7..58c24f0710 100644
--- a/src/Avalonia.Controls/WindowBase.cs
+++ b/src/Avalonia.Controls/WindowBase.cs
@@ -224,16 +224,53 @@ namespace Avalonia.Controls
         /// <param name="clientSize">The new client size.</param>
         protected override void HandleResized(Size clientSize)
         {
-            if (!AutoSizing)
-            {
-                Width = clientSize.Width;
-                Height = clientSize.Height;
-            }
             ClientSize = clientSize;
             LayoutManager.ExecuteLayoutPass();
             Renderer?.Resized(clientSize);
         }
 
+        /// <summary>
+        /// Overrides the core measure logic for windows.
+        /// </summary>
+        /// <param name="availableSize">The available size.</param>
+        /// <returns>The measured size.</returns>
+        /// <remarks>
+        /// The layout logic for top-level windows is different than for other controls because
+        /// they don't have a parent, meaning that many layout properties handled by the default
+        /// MeasureCore (such as margins and alignment) make no sense.
+        /// </remarks>
+        protected override Size MeasureCore(Size availableSize)
+        {
+            ApplyTemplate();
+
+            var constraint = LayoutHelper.ApplyLayoutConstraints(this, availableSize);
+
+            return MeasureOverride(constraint);
+        }
+
+        /// <summary>
+        /// Overrides the core arrange logic for windows.
+        /// </summary>
+        /// <param name="finalRect">The final arrange rect.</param>
+        /// <remarks>
+        /// The layout logic for top-level windows is different than for other controls because
+        /// they don't have a parent, meaning that many layout properties handled by the default
+        /// ArrangeCore (such as margins and alignment) make no sense.
+        /// </remarks>
+        protected override void ArrangeCore(Rect finalRect)
+        {
+            var constraint = ArrangeSetBounds(finalRect.Size);
+            var arrangeSize = ArrangeOverride(constraint);
+            Bounds = new Rect(arrangeSize);
+        }
+
+        /// <summary>
+        /// Called durung the arrange pass to set the size of the window.
+        /// </summary>
+        /// <param name="size">The requested size of the window.</param>
+        /// <returns>The actual size of the window.</returns>
+        protected virtual Size ArrangeSetBounds(Size size) => size;
+
         /// <summary>
         /// Handles a window position change notification from 
         /// <see cref="IWindowBaseImpl.PositionChanged"/>.
@@ -255,7 +292,7 @@ namespace Avalonia.Controls
 
             if (scope != null)
             {
-                FocusManager.Instance.SetFocusScope(scope);
+                FocusManager.Instance?.SetFocusScope(scope);
             }
 
             IsActive = true;
diff --git a/src/Avalonia.Dialogs/ManagedFileChooser.xaml b/src/Avalonia.Dialogs/ManagedFileChooser.xaml
index af0c91e7bd..8a0451f982 100644
--- a/src/Avalonia.Dialogs/ManagedFileChooser.xaml
+++ b/src/Avalonia.Dialogs/ManagedFileChooser.xaml
@@ -58,7 +58,7 @@
             <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Spacing="10">
                 <StackPanel.Styles>
                     <Style Selector="Button">
-                        <Setter Property="Margin">4</Setter>
+                        <Setter Property="Margin" Value="4"/>
                     </Style>
                 </StackPanel.Styles>
                 <Button Command="{Binding Ok}">OK</Button>
diff --git a/src/Avalonia.Dialogs/ManagedFileChooserViewModel.cs b/src/Avalonia.Dialogs/ManagedFileChooserViewModel.cs
index 189e13802d..1e2d15ab70 100644
--- a/src/Avalonia.Dialogs/ManagedFileChooserViewModel.cs
+++ b/src/Avalonia.Dialogs/ManagedFileChooserViewModel.cs
@@ -14,6 +14,7 @@ namespace Avalonia.Dialogs
 {
     internal class ManagedFileChooserViewModel : InternalViewModelBase
     {
+        private readonly ManagedFileDialogOptions _options;
         public event Action CancelRequested;
         public event Action<string[]> CompleteRequested;
 
@@ -103,8 +104,9 @@ namespace Avalonia.Dialogs
             QuickLinks.AddRange(quickSources.GetAllItems().Select(i => new ManagedFileChooserItemViewModel(i)));
         }
 
-        public ManagedFileChooserViewModel(FileSystemDialog dialog)
+        public ManagedFileChooserViewModel(FileSystemDialog dialog, ManagedFileDialogOptions options)
         {
+            _options = options;
             _disposables = new CompositeDisposable();
 
             var quickSources = AvaloniaLocator.Current
@@ -202,10 +204,12 @@ namespace Avalonia.Dialogs
                     }
                     else
                     {
-                        var invalidItems = SelectedItems.Where(i => i.ItemType == ManagedFileChooserItemType.Folder).ToList();
-                        foreach (var item in invalidItems)
+                        if (!_options.AllowDirectorySelection)
                         {
-                            SelectedItems.Remove(item);
+                            var invalidItems = SelectedItems.Where(i => i.ItemType == ManagedFileChooserItemType.Folder)
+                                .ToList();
+                            foreach (var item in invalidItems) 
+                                SelectedItems.Remove(item);
                         }
 
                         if (!_selectingDirectory)
diff --git a/src/Avalonia.Dialogs/ManagedFileDialogExtensions.cs b/src/Avalonia.Dialogs/ManagedFileDialogExtensions.cs
index 771d2b1b5e..fa85f28591 100644
--- a/src/Avalonia.Dialogs/ManagedFileDialogExtensions.cs
+++ b/src/Avalonia.Dialogs/ManagedFileDialogExtensions.cs
@@ -13,13 +13,15 @@ namespace Avalonia.Dialogs
     {
         class ManagedSystemDialogImpl<T> : ISystemDialogImpl where T : Window, new()
         {
-            async Task<string[]> Show(SystemDialog d, IWindowImpl parent)
+            async Task<string[]> Show(SystemDialog d, IWindowImpl parent, ManagedFileDialogOptions options = null)
             {
-                var model = new ManagedFileChooserViewModel((FileSystemDialog)d);
+                var model = new ManagedFileChooserViewModel((FileSystemDialog)d,
+                    options ?? new ManagedFileDialogOptions());
 
                 var dialog = new T
                 {
                     Content = new ManagedFileChooser(),
+                    Title = d.Title,
                     DataContext = model
                 };
 
@@ -48,6 +50,11 @@ namespace Avalonia.Dialogs
             {
                 return (await Show(dialog, parent))?.FirstOrDefault();
             }
+            
+            public async Task<string[]> ShowFileDialogAsync(FileDialog dialog, Window parent, ManagedFileDialogOptions options)
+            {
+                return await Show(dialog, parent.PlatformImpl, options);
+            }
         }
 
         public static TAppBuilder UseManagedSystemDialogs<TAppBuilder>(this TAppBuilder builder)
@@ -65,5 +72,14 @@ namespace Avalonia.Dialogs
                 AvaloniaLocator.CurrentMutable.Bind<ISystemDialogImpl>().ToSingleton<ManagedSystemDialogImpl<TWindow>>());
             return builder;
         }
+
+        public static Task<string[]> ShowManagedAsync(this OpenFileDialog dialog, Window parent,
+            ManagedFileDialogOptions options = null) => ShowManagedAsync<Window>(dialog, parent, options);
+        
+        public static Task<string[]> ShowManagedAsync<TWindow>(this OpenFileDialog dialog, Window parent,
+            ManagedFileDialogOptions options = null) where TWindow : Window, new()
+        {
+            return new ManagedSystemDialogImpl<TWindow>().ShowFileDialogAsync(dialog, parent, options);
+        }
     }
 }
diff --git a/src/Avalonia.Dialogs/ManagedFileDialogOptions.cs b/src/Avalonia.Dialogs/ManagedFileDialogOptions.cs
new file mode 100644
index 0000000000..56a3eb9122
--- /dev/null
+++ b/src/Avalonia.Dialogs/ManagedFileDialogOptions.cs
@@ -0,0 +1,7 @@
+namespace Avalonia.Dialogs
+{
+    public class ManagedFileDialogOptions
+    {
+        public bool AllowDirectorySelection { get; set; }
+    }
+}
diff --git a/src/Avalonia.Input/FocusManager.cs b/src/Avalonia.Input/FocusManager.cs
index 97b2f7a397..8c9e677726 100644
--- a/src/Avalonia.Input/FocusManager.cs
+++ b/src/Avalonia.Input/FocusManager.cs
@@ -171,7 +171,7 @@ namespace Avalonia.Input
             {
                 var scope = control as IFocusScope;
 
-                if (scope != null)
+                if (scope != null && control.VisualRoot?.IsVisible == true)
                 {
                     yield return scope;
                 }
diff --git a/src/Avalonia.Input/GestureRecognizers/ScrollGestureRecognizer.cs b/src/Avalonia.Input/GestureRecognizers/ScrollGestureRecognizer.cs
index 4f3c7c0bba..a582fae8b5 100644
--- a/src/Avalonia.Input/GestureRecognizers/ScrollGestureRecognizer.cs
+++ b/src/Avalonia.Input/GestureRecognizers/ScrollGestureRecognizer.cs
@@ -148,6 +148,7 @@ namespace Avalonia.Input.GestureRecognizers
                     EndGesture();
                 else
                 {
+                    _tracking = null;
                     var savedGestureId = _gestureId;
                     var st = Stopwatch.StartNew();
                     var lastTime = TimeSpan.Zero;
diff --git a/src/Avalonia.Input/Raw/RawPointerEventArgs.cs b/src/Avalonia.Input/Raw/RawPointerEventArgs.cs
index 56854c7d29..29c636a01a 100644
--- a/src/Avalonia.Input/Raw/RawPointerEventArgs.cs
+++ b/src/Avalonia.Input/Raw/RawPointerEventArgs.cs
@@ -62,7 +62,7 @@ namespace Avalonia.Input.Raw
         /// <summary>
         /// Gets the type of the event.
         /// </summary>
-        public RawPointerEventType Type { get; private set; }
+        public RawPointerEventType Type { get; set; }
 
         /// <summary>
         /// Gets the input modifiers.
diff --git a/src/Avalonia.Layout/LayoutHelper.cs b/src/Avalonia.Layout/LayoutHelper.cs
index d77cc269f9..65a6d9047e 100644
--- a/src/Avalonia.Layout/LayoutHelper.cs
+++ b/src/Avalonia.Layout/LayoutHelper.cs
@@ -2,6 +2,8 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Layout
 {
@@ -21,13 +23,11 @@ namespace Avalonia.Layout
         /// <returns>The control's size.</returns>
         public static Size ApplyLayoutConstraints(ILayoutable control, Size constraints)
         {
-            double width = (control.Width > 0) ? control.Width : constraints.Width;
-            double height = (control.Height > 0) ? control.Height : constraints.Height;
-            width = Math.Min(width, control.MaxWidth);
-            width = Math.Max(width, control.MinWidth);
-            height = Math.Min(height, control.MaxHeight);
-            height = Math.Max(height, control.MinHeight);
-            return new Size(width, height);
+            var minmax = new MinMax(control);
+
+            return new Size(
+                MathUtilities.Clamp(constraints.Width, minmax.MinWidth, minmax.MaxWidth),
+                MathUtilities.Clamp(constraints.Height, minmax.MinHeight, minmax.MaxHeight));
         }
 
         public static Size MeasureChild(ILayoutable control, Size availableSize, Thickness padding,
@@ -58,5 +58,65 @@ namespace Avalonia.Layout
 
             return availableSize;
         }
+
+        /// <summary>
+        /// Invalidates measure for given control and all visual children recursively.
+        /// </summary>
+        public static void InvalidateSelfAndChildrenMeasure(ILayoutable control)
+        {
+            void InnerInvalidateMeasure(IVisual target)
+            {
+                if (target is ILayoutable targetLayoutable)
+                {
+                    targetLayoutable.InvalidateMeasure();
+                }
+
+                var visualChildren = target.VisualChildren;
+                var visualChildrenCount = visualChildren.Count;
+
+                for (int i = 0; i < visualChildrenCount; i++)
+                {
+                    IVisual child = visualChildren[i];
+
+                    InnerInvalidateMeasure(child);
+                }
+            }
+
+            InnerInvalidateMeasure(control);
+        }
+
+        /// <summary>
+        /// Calculates the min and max height for a control. Ported from WPF.
+        /// </summary>
+        private readonly struct MinMax
+        {
+            public MinMax(ILayoutable e)
+            {
+                MaxHeight = e.MaxHeight;
+                MinHeight = e.MinHeight;
+                double l = e.Height;
+
+                double height = (double.IsNaN(l) ? double.PositiveInfinity : l);
+                MaxHeight = Math.Max(Math.Min(height, MaxHeight), MinHeight);
+
+                height = (double.IsNaN(l) ? 0 : l);
+                MinHeight = Math.Max(Math.Min(MaxHeight, height), MinHeight);
+
+                MaxWidth = e.MaxWidth;
+                MinWidth = e.MinWidth;
+                l = e.Width;
+
+                double width = (double.IsNaN(l) ? double.PositiveInfinity : l);
+                MaxWidth = Math.Max(Math.Min(width, MaxWidth), MinWidth);
+
+                width = (double.IsNaN(l) ? 0 : l);
+                MinWidth = Math.Max(Math.Min(MaxWidth, width), MinWidth);
+            }
+
+            public double MinWidth { get; }
+            public double MaxWidth { get; }
+            public double MinHeight { get; }
+            public double MaxHeight { get; }
+        }
     }
 }
diff --git a/src/Avalonia.Layout/LayoutManager.cs b/src/Avalonia.Layout/LayoutManager.cs
index 855f123748..917f5408d9 100644
--- a/src/Avalonia.Layout/LayoutManager.cs
+++ b/src/Avalonia.Layout/LayoutManager.cs
@@ -126,8 +126,16 @@ namespace Avalonia.Layout
         /// <inheritdoc/>
         public void ExecuteInitialLayoutPass(ILayoutRoot root)
         {
-            Measure(root);
-            Arrange(root);
+            try
+            {
+                _running = true;
+                Measure(root);
+                Arrange(root);
+            }
+            finally
+            {
+                _running = false;
+            }
 
             // Running the initial layout pass may have caused some control to be invalidated
             // so run a full layout pass now (this usually due to scrollbars; its not known
diff --git a/src/Avalonia.Native/WindowImplBase.cs b/src/Avalonia.Native/WindowImplBase.cs
index 322cbe8371..ee171e45ef 100644
--- a/src/Avalonia.Native/WindowImplBase.cs
+++ b/src/Avalonia.Native/WindowImplBase.cs
@@ -170,9 +170,12 @@ namespace Avalonia.Native
 
             void IAvnWindowBaseEvents.Resized(AvnSize size)
             {
-                var s = new Size(size.Width, size.Height);
-                _parent._savedLogicalSize = s;
-                _parent.Resized?.Invoke(s);
+                if (_parent._native != null)
+                {
+                    var s = new Size(size.Width, size.Height);
+                    _parent._savedLogicalSize = s;
+                    _parent.Resized?.Invoke(s);
+                }
             }
 
             void IAvnWindowBaseEvents.PositionChanged(AvnPoint position)
@@ -333,7 +336,7 @@ namespace Avalonia.Native
             _native.SetTopMost(value);
         }
 
-        public double Scaling => _native.GetScaling();
+        public double Scaling => _native?.GetScaling() ?? 1;
 
         public Action Deactivated { get; set; }
         public Action Activated { get; set; }
diff --git a/src/Avalonia.ReactiveUI/AppBuilderExtensions.cs b/src/Avalonia.ReactiveUI/AppBuilderExtensions.cs
index ced26a3004..eb8bd10082 100644
--- a/src/Avalonia.ReactiveUI/AppBuilderExtensions.cs
+++ b/src/Avalonia.ReactiveUI/AppBuilderExtensions.cs
@@ -18,7 +18,7 @@ namespace Avalonia.ReactiveUI
         public static TAppBuilder UseReactiveUI<TAppBuilder>(this TAppBuilder builder)
             where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
         {
-            return builder.AfterSetup(_ =>
+            return builder.AfterPlatformServicesSetup(_ =>
             {
                 RxApp.MainThreadScheduler = AvaloniaScheduler.Instance;
                 Locator.CurrentMutable.RegisterConstant(new AvaloniaActivationForViewFetcher(), typeof(IActivationForViewFetcher));
diff --git a/src/Avalonia.Themes.Default/TreeViewItem.xaml b/src/Avalonia.Themes.Default/TreeViewItem.xaml
index 0d826806d0..a3f8d8b7f7 100644
--- a/src/Avalonia.Themes.Default/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Default/TreeViewItem.xaml
@@ -17,8 +17,7 @@
                             BorderThickness="{TemplateBinding BorderThickness}"
                             TemplatedControl.IsTemplateFocusTarget="True">
                         <Grid Name="PART_Header"
-                              ColumnDefinitions="16, Auto"
-                              HorizontalAlignment="Left"
+                              ColumnDefinitions="16, *"
                               Margin="{TemplateBinding Level, Mode=OneWay, Converter={StaticResource LeftMarginConverter}}" >
                             <ToggleButton Name="expander"
                                           Focusable="False"
diff --git a/src/Avalonia.X11/NativeDialogs/Gtk.cs b/src/Avalonia.X11/NativeDialogs/Gtk.cs
index a26f049f0d..82cf3c934f 100644
--- a/src/Avalonia.X11/NativeDialogs/Gtk.cs
+++ b/src/Avalonia.X11/NativeDialogs/Gtk.cs
@@ -190,6 +190,9 @@ namespace Avalonia.X11.NativeDialogs
         [DllImport(GtkName)]
         public static extern void gtk_file_chooser_set_filename(IntPtr chooser, Utf8Buffer file);
 
+        [DllImport(GtkName)]
+        public static extern void gtk_file_chooser_set_current_name(IntPtr chooser, Utf8Buffer file);
+        
         [DllImport(GtkName)]
         public static extern IntPtr gtk_file_filter_new();
         
diff --git a/src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs b/src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs
index ffd1c1b57e..5c9a0c992a 100644
--- a/src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs
+++ b/src/Avalonia.X11/NativeDialogs/GtkNativeFileDialogs.cs
@@ -91,7 +91,13 @@ namespace Avalonia.X11.NativeDialogs
                 gtk_dialog_add_button(dlg, open, GtkResponseType.Cancel);
             if (initialFileName != null)
                 using (var fn = new Utf8Buffer(initialFileName))
-                    gtk_file_chooser_set_filename(dlg, fn);
+                {
+                    if (action == GtkFileChooserAction.Save)
+                        gtk_file_chooser_set_current_name(dlg, fn);
+                    else
+                        gtk_file_chooser_set_filename(dlg, fn);
+                }
+
             gtk_window_present(dlg);
             return tcs.Task;
         }
diff --git a/src/Avalonia.X11/X11ImmediateRendererProxy.cs b/src/Avalonia.X11/X11ImmediateRendererProxy.cs
new file mode 100644
index 0000000000..8fee6d7175
--- /dev/null
+++ b/src/Avalonia.X11/X11ImmediateRendererProxy.cs
@@ -0,0 +1,110 @@
+using System;
+using System.Collections.Generic;
+using Avalonia.Rendering;
+using Avalonia.Threading;
+using Avalonia.VisualTree;
+
+namespace Avalonia.X11
+{
+    public class X11ImmediateRendererProxy : IRenderer, IRenderLoopTask
+    {
+        private readonly IRenderLoop _loop;
+        private ImmediateRenderer _renderer;
+        private bool _invalidated;
+        private bool _running;
+        private object _lock = new object();
+
+        public X11ImmediateRendererProxy(IVisual root, IRenderLoop loop)
+        {
+            _loop = loop;
+            _renderer = new ImmediateRenderer(root);
+            
+        }
+
+        public void Dispose()
+        {
+            _running = false;
+            _renderer.Dispose();
+        }
+
+        public bool DrawFps
+        {
+            get => _renderer.DrawFps;
+            set => _renderer.DrawFps = value;
+        }
+
+        public bool DrawDirtyRects
+        {
+            get => _renderer.DrawDirtyRects;
+            set => _renderer.DrawDirtyRects = value;
+        }
+
+        public event EventHandler<SceneInvalidatedEventArgs> SceneInvalidated
+        {
+            add => _renderer.SceneInvalidated += value;
+            remove => _renderer.SceneInvalidated -= value;
+        }
+
+        public void AddDirty(IVisual visual)
+        {
+            lock (_lock)
+                _invalidated = true;
+            _renderer.AddDirty(visual);
+        }
+
+        public IEnumerable<IVisual> HitTest(Point p, IVisual root, Func<IVisual, bool> filter)
+        {
+            return _renderer.HitTest(p, root, filter);
+        }
+
+        public void RecalculateChildren(IVisual visual)
+        {
+            _renderer.RecalculateChildren(visual);
+        }
+
+        public void Resized(Size size)
+        {
+            _renderer.Resized(size);
+        }
+
+        public void Paint(Rect rect)
+        {
+            _invalidated = false;
+            _renderer.Paint(rect);
+        }
+
+        public void Start()
+        {
+            _running = true;
+            _loop.Add(this);
+            _renderer.Start();
+        }
+
+        public void Stop()
+        {
+            _running = false;
+            _loop.Remove(this);
+            _renderer.Stop();
+        }
+
+        public bool NeedsUpdate => false;
+        public void Update(TimeSpan time)
+        {
+            
+        }
+
+        public void Render()
+        {
+            if (_invalidated)
+            {
+                lock (_lock)
+                    _invalidated = false;
+                Dispatcher.UIThread.Post(() =>
+                {
+                    if (_running)
+                        Paint(new Rect(0, 0, 100000, 100000));
+                });
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.X11/X11Platform.cs b/src/Avalonia.X11/X11Platform.cs
index e53197b10c..694c8cd165 100644
--- a/src/Avalonia.X11/X11Platform.cs
+++ b/src/Avalonia.X11/X11Platform.cs
@@ -99,6 +99,7 @@ namespace Avalonia
         public bool UseGpu { get; set; } = true;
         public bool OverlayPopups { get; set; }
         public bool UseDBusMenu { get; set; }
+        public bool UseDeferredRendering { get; set; } = true;
 
         public List<string> GlxRendererBlacklist { get; set; } = new List<string>
         {
diff --git a/src/Avalonia.X11/X11Window.cs b/src/Avalonia.X11/X11Window.cs
index 22a04450bb..8406caab1c 100644
--- a/src/Avalonia.X11/X11Window.cs
+++ b/src/Avalonia.X11/X11Window.cs
@@ -29,7 +29,6 @@ namespace Avalonia.X11
         private readonly IWindowImpl _popupParent;
         private readonly bool _popup;
         private readonly X11Info _x11;
-        private bool _invalidated;
         private XConfigureEvent? _configure;
         private PixelPoint? _configurePoint;
         private bool _triggeredExpose;
@@ -306,8 +305,13 @@ namespace Avalonia.X11
         public Action Closed { get; set; }
         public Action<PixelPoint> PositionChanged { get; set; }
 
-        public IRenderer CreateRenderer(IRenderRoot root) =>
-            new DeferredRenderer(root, AvaloniaLocator.Current.GetService<IRenderLoop>());
+        public IRenderer CreateRenderer(IRenderRoot root)
+        {
+            var loop = AvaloniaLocator.Current.GetService<IRenderLoop>();
+            return _platform.Options.UseDeferredRendering ?
+                new DeferredRenderer(root, loop) :
+                (IRenderer)new X11ImmediateRendererProxy(root, loop);
+        }
 
         void OnEvent(XEvent ev)
         {
@@ -421,7 +425,7 @@ namespace Avalonia.X11
                             updatedSizeViaScaling = UpdateScaling();
                         }
 
-                        if (changedSize && !updatedSizeViaScaling)
+                        if (changedSize && !updatedSizeViaScaling && !_popup)
                             Resized?.Invoke(ClientSize);
 
                         Dispatcher.UIThread.RunJobs(DispatcherPriority.Layout);
@@ -530,14 +534,14 @@ namespace Avalonia.X11
                 }
                 else if (value == WindowState.Maximized)
                 {
-                    SendNetWMMessage(_x11.Atoms._NET_WM_STATE, (IntPtr)0, _x11.Atoms._NET_WM_STATE_HIDDEN, IntPtr.Zero);
-                    SendNetWMMessage(_x11.Atoms._NET_WM_STATE, (IntPtr)1, _x11.Atoms._NET_WM_STATE_MAXIMIZED_VERT,
+                    ChangeWMAtoms(false, _x11.Atoms._NET_WM_STATE_HIDDEN);
+                    ChangeWMAtoms(true, _x11.Atoms._NET_WM_STATE_MAXIMIZED_VERT,
                         _x11.Atoms._NET_WM_STATE_MAXIMIZED_HORZ);
                 }
                 else
                 {
-                    SendNetWMMessage(_x11.Atoms._NET_WM_STATE, (IntPtr)0, _x11.Atoms._NET_WM_STATE_HIDDEN, IntPtr.Zero);
-                    SendNetWMMessage(_x11.Atoms._NET_WM_STATE, (IntPtr)0, _x11.Atoms._NET_WM_STATE_MAXIMIZED_VERT,
+                    ChangeWMAtoms(false, _x11.Atoms._NET_WM_STATE_HIDDEN);
+                    ChangeWMAtoms(false, _x11.Atoms._NET_WM_STATE_MAXIMIZED_VERT,
                         _x11.Atoms._NET_WM_STATE_MAXIMIZED_HORZ);
                 }
             }
@@ -624,7 +628,27 @@ namespace Avalonia.X11
             ScheduleInput(args);
         }
 
-        public void ScheduleInput(RawInputEventArgs args)
+        public void ScheduleXI2Input(RawInputEventArgs args)
+        {
+            if (args is RawPointerEventArgs pargs)
+            {
+                if ((pargs.Type == RawPointerEventType.TouchBegin
+                     || pargs.Type == RawPointerEventType.TouchUpdate
+                     || pargs.Type == RawPointerEventType.LeftButtonDown
+                     || pargs.Type == RawPointerEventType.RightButtonDown
+                     || pargs.Type == RawPointerEventType.MiddleButtonDown
+                     || pargs.Type == RawPointerEventType.NonClientLeftButtonDown)
+                    && ActivateTransientChildIfNeeded())
+                    return;
+                if (pargs.Type == RawPointerEventType.TouchEnd
+                    && ActivateTransientChildIfNeeded())
+                    pargs.Type = RawPointerEventType.TouchCancel;
+            }
+
+            ScheduleInput(args);
+        }
+        
+        private void ScheduleInput(RawInputEventArgs args)
         {
             if (args is RawPointerEventArgs mouse)
                 mouse.Position = mouse.Position / Scaling;
@@ -663,20 +687,12 @@ namespace Avalonia.X11
 
         void DoPaint()
         {
-            _invalidated = false;
             Paint?.Invoke(new Rect());
         }
         
         public void Invalidate(Rect rect)
         {
-            if(_invalidated)
-                return;
-            _invalidated = true;
-            Dispatcher.UIThread.InvokeAsync(() =>
-            {
-                if (_mapped)
-                    DoPaint();
-            });
+
         }
 
         public IInputRoot InputRoot => _inputRoot;
@@ -738,7 +754,15 @@ namespace Avalonia.X11
             _transientParent = window;
             _transientParent?._transientChildren.Add(this);
             if (informServer)
-                XSetTransientForHint(_x11.Display, _handle, _transientParent?._handle ?? IntPtr.Zero);
+                SetTransientForHint(_transientParent?._handle);
+        }
+
+        void SetTransientForHint(IntPtr? parent)
+        {
+            if (parent == null || parent == IntPtr.Zero)
+                XDeleteProperty(_x11.Display, _handle, _x11.Atoms.XA_WM_TRANSIENT_FOR);
+            else
+                XSetTransientForHint(_x11.Display, _handle, parent.Value);
         }
 
         public void Show()
@@ -968,8 +992,7 @@ namespace Avalonia.X11
 
         public void SetTopmost(bool value)
         {
-            SendNetWMMessage(_x11.Atoms._NET_WM_STATE,
-                (IntPtr)(value ? 1 : 0), _x11.Atoms._NET_WM_STATE_ABOVE, IntPtr.Zero);
+            ChangeWMAtoms(value, _x11.Atoms._NET_WM_STATE_ABOVE);
         }
 
         public void ShowDialog(IWindowImpl parent)
@@ -980,17 +1003,57 @@ namespace Avalonia.X11
 
         public void SetIcon(IWindowIconImpl icon)
         {
-            var data = ((X11IconData)icon).Data;
-            fixed (void* pdata = data)
-                XChangeProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_ICON,
-                    new IntPtr((int)Atom.XA_CARDINAL), 32, PropertyMode.Replace,
-                    pdata, data.Length);
+            if (icon != null)
+            {
+                var data = ((X11IconData)icon).Data;
+                fixed (void* pdata = data)
+                    XChangeProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_ICON,
+                        new IntPtr((int)Atom.XA_CARDINAL), 32, PropertyMode.Replace,
+                        pdata, data.Length);
+            }
+            else
+            {
+                XDeleteProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_ICON);
+            }
         }
 
         public void ShowTaskbarIcon(bool value)
         {
+            ChangeWMAtoms(!value, _x11.Atoms._NET_WM_STATE_SKIP_TASKBAR);
+        }
+
+        void ChangeWMAtoms(bool enable, params IntPtr[] atoms)
+        {
+            if (atoms.Length < 1 || atoms.Length > 4)
+                throw new ArgumentException();
+
+            if (!_mapped)
+            {
+                XGetWindowProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_STATE, IntPtr.Zero, new IntPtr(256),
+                    false, (IntPtr)Atom.XA_ATOM, out _, out _, out var nitems, out _,
+                    out var prop);
+                var ptr = (IntPtr*)prop.ToPointer();
+                var newAtoms = new HashSet<IntPtr>();
+                for (var c = 0; c < nitems.ToInt64(); c++) 
+                    newAtoms.Add(*ptr);
+                XFree(prop);
+                foreach(var atom in atoms)
+                    if (enable)
+                        newAtoms.Add(atom);
+                    else
+                        newAtoms.Remove(atom);
+
+                XChangeProperty(_x11.Display, _handle, _x11.Atoms._NET_WM_STATE, (IntPtr)Atom.XA_ATOM, 32,
+                    PropertyMode.Replace, newAtoms.ToArray(), newAtoms.Count);
+            }
+            
             SendNetWMMessage(_x11.Atoms._NET_WM_STATE,
-                (IntPtr)(value ? 0 : 1), _x11.Atoms._NET_WM_STATE_SKIP_TASKBAR, IntPtr.Zero);
+                (IntPtr)(enable ? 1 : 0),
+                atoms[0],
+                atoms.Length > 1 ? atoms[1] : IntPtr.Zero,
+                atoms.Length > 2 ? atoms[2] : IntPtr.Zero,
+                atoms.Length > 3 ? atoms[3] : IntPtr.Zero
+            );
         }
 
         public IPopupPositioner PopupPositioner { get; }
diff --git a/src/Avalonia.X11/XI2Manager.cs b/src/Avalonia.X11/XI2Manager.cs
index e37ed39bee..55e8d43e24 100644
--- a/src/Avalonia.X11/XI2Manager.cs
+++ b/src/Avalonia.X11/XI2Manager.cs
@@ -196,7 +196,7 @@ namespace Avalonia.X11
                     (ev.Type == XiEventType.XI_TouchUpdate ?
                         RawPointerEventType.TouchUpdate :
                         RawPointerEventType.TouchEnd);
-                client.ScheduleInput(new RawTouchEventArgs(client.TouchDevice,
+                client.ScheduleXI2Input(new RawTouchEventArgs(client.TouchDevice,
                     ev.Timestamp, client.InputRoot, type, ev.Position, ev.Modifiers, ev.Detail));
                 return;
             }
@@ -230,10 +230,10 @@ namespace Avalonia.X11
                 }
 
                 if (scrollDelta != default)
-                    client.ScheduleInput(new RawMouseWheelEventArgs(client.MouseDevice, ev.Timestamp,
+                    client.ScheduleXI2Input(new RawMouseWheelEventArgs(client.MouseDevice, ev.Timestamp,
                         client.InputRoot, ev.Position, scrollDelta, ev.Modifiers));
                 if (_pointerDevice.HasMotion(ev))
-                    client.ScheduleInput(new RawPointerEventArgs(client.MouseDevice, ev.Timestamp, client.InputRoot,
+                    client.ScheduleXI2Input(new RawPointerEventArgs(client.MouseDevice, ev.Timestamp, client.InputRoot,
                         RawPointerEventType.Move, ev.Position, ev.Modifiers));
             }
 
@@ -246,7 +246,7 @@ namespace Avalonia.X11
                     : ev.Button == 3 ? (down ? RawPointerEventType.RightButtonDown : RawPointerEventType.RightButtonUp)
                     : (RawPointerEventType?)null;
                 if (type.HasValue)
-                    client.ScheduleInput(new RawPointerEventArgs(client.MouseDevice, ev.Timestamp, client.InputRoot,
+                    client.ScheduleXI2Input(new RawPointerEventArgs(client.MouseDevice, ev.Timestamp, client.InputRoot,
                         type.Value, ev.Position, ev.Modifiers));
             }
             
@@ -307,7 +307,7 @@ namespace Avalonia.X11
     interface IXI2Client
     {
         IInputRoot InputRoot { get; }
-        void ScheduleInput(RawInputEventArgs args);
+        void ScheduleXI2Input(RawInputEventArgs args);
         IMouseDevice MouseDevice { get; }
         TouchDevice TouchDevice { get; }
     }
diff --git a/src/Markup/Avalonia.Markup.Xaml/XamlIl/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs b/src/Markup/Avalonia.Markup.Xaml/XamlIl/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
index aac07f5b6e..d5114244cf 100644
--- a/src/Markup/Avalonia.Markup.Xaml/XamlIl/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/XamlIl/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
@@ -104,6 +104,11 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                     }
                 }
 
+                if (results != null && result != null)
+                {
+                    results.Add(result);
+                }
+
                 return results ?? result;
             }
 
@@ -158,9 +163,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
         protected void EmitCall(XamlIlEmitContext context, IXamlIlEmitter codeGen, Func<IXamlIlMethod, bool> method)
         {
             var selectors = context.Configuration.TypeSystem.GetType("Avalonia.Styling.Selectors");
-            var found = selectors.FindMethod(m => m.IsStatic && m.Parameters.Count > 0 &&
-                                      m.Parameters[0].FullName == "Avalonia.Styling.Selector"
-                                      && method(m));
+            var found = selectors.FindMethod(m => m.IsStatic && m.Parameters.Count > 0 && method(m));
             codeGen.EmitCall(found);
         }
     }
@@ -308,8 +311,35 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             _selectors.Add(node);
         }
         
-        //TODO: actually find the type
-        public override IXamlIlType TargetType => _selectors.FirstOrDefault()?.TargetType;
+        public override IXamlIlType TargetType
+        {
+            get
+            {
+                IXamlIlType result = null;
+
+                foreach (var selector in _selectors)
+                {
+                    if (selector.TargetType == null)
+                    {
+                        return null;
+                    }
+                    else if (result == null)
+                    {
+                        result = selector.TargetType;
+                    }
+                    else
+                    {
+                        while (!result.IsAssignableFrom(selector.TargetType))
+                        {
+                            result = result.BaseType;
+                        }
+                    }
+                }
+
+                return result;
+            }
+        }
+
         protected override void DoEmit(XamlIlEmitContext context, IXamlIlEmitter codeGen)
         {
             if (_selectors.Count == 0)
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index a8554bce6e..cb0001b509 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -940,7 +940,7 @@ namespace Avalonia.Win32
         public void SetIcon(IWindowIconImpl icon)
         {
             var impl = (IconImpl)icon;
-            var hIcon = impl.HIcon;
+            var hIcon = impl?.HIcon ?? IntPtr.Zero;
             UnmanagedMethods.PostMessage(_hwnd, (int)UnmanagedMethods.WindowsMessage.WM_SETICON,
                 new IntPtr((int)UnmanagedMethods.Icons.ICON_BIG), hIcon);
         }
diff --git a/tests/Avalonia.Animation.UnitTests/Avalonia.Animation.UnitTests.csproj b/tests/Avalonia.Animation.UnitTests/Avalonia.Animation.UnitTests.csproj
index ef515ce155..dd50eff2b6 100644
--- a/tests/Avalonia.Animation.UnitTests/Avalonia.Animation.UnitTests.csproj
+++ b/tests/Avalonia.Animation.UnitTests/Avalonia.Animation.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj b/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
index 6e885f33be..0d87f0eb03 100644
--- a/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
+++ b/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_MultiBinding.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_MultiBinding.cs
new file mode 100644
index 0000000000..757160a0a4
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_MultiBinding.cs
@@ -0,0 +1,178 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Reactive.Linq;
+using System.Reactive.Subjects;
+using Avalonia.Data;
+using Avalonia.Data.Converters;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests
+{
+    public class AvaloniaObjectTests_MultiBinding
+    {
+        [Fact]
+        public void Should_Update()
+        {
+            var target = new Class1();
+
+            var b = new Subject<object>();
+
+            var mb = new MultiBinding()
+            {
+                Converter = StringJoinConverter,
+                Bindings = new[]
+                {
+                    b.ToBinding()
+                }
+            };
+            target.Bind(Class1.FooProperty, mb);
+
+            Assert.Equal(null, target.Foo);
+
+            b.OnNext("Foo");
+
+            Assert.Equal("Foo", target.Foo);
+
+            b.OnNext("Bar");
+
+            Assert.Equal("Bar", target.Foo);
+        }
+
+        [Fact]
+        public void Should_Update_With_Multiple_Bindings()
+        {
+            var target = new Class1();
+
+            var bindings = Enumerable.Range(0, 3).Select(i => new BehaviorSubject<object>("Empty")).ToArray();
+
+            var mb = new MultiBinding()
+            {
+                Converter = StringJoinConverter,
+                Bindings = bindings.Select(b => b.ToBinding()).ToArray()
+            };
+            target.Bind(Class1.FooProperty, mb);
+
+            Assert.Equal("Empty,Empty,Empty", target.Foo);
+
+            bindings[0].OnNext("Foo");
+
+            Assert.Equal("Foo,Empty,Empty", target.Foo);
+
+            bindings[1].OnNext("Bar");
+
+            Assert.Equal("Foo,Bar,Empty", target.Foo);
+
+            bindings[2].OnNext("Baz");
+
+            Assert.Equal("Foo,Bar,Baz", target.Foo);
+        }
+
+        [Fact]
+        public void Should_Update_When_Null_Value_In_Bindings()
+        {
+            var target = new Class1();
+
+            var b = new Subject<object>();
+
+            var mb = new MultiBinding()
+            {
+                Converter = StringJoinConverter,
+                Bindings = new[]
+                {
+                    b.ToBinding()
+                }
+            };
+            target.Bind(Class1.FooProperty, mb);
+
+            Assert.Equal(null, target.Foo);
+
+            b.OnNext("Foo");
+
+            Assert.Equal("Foo", target.Foo);
+
+            b.OnNext(null);
+
+            Assert.Equal("", target.Foo);
+        }
+
+        [Fact]
+        public void Should_Update_When_Null_Value_In_Bindings_With_StringFormat()
+        {
+            var target = new Class1();
+
+            var b = new Subject<object>();
+
+            var mb = new MultiBinding()
+            {
+                StringFormat = "Converted: {0}",
+                Bindings = new[]
+                {
+                    b.ToBinding()
+                }
+            };
+            target.Bind(Class1.FooProperty, mb);
+
+            Assert.Equal(null, target.Foo);
+            b.OnNext("Foo");
+            Assert.Equal("Converted: Foo", target.Foo);
+            b.OnNext(null);
+            Assert.Equal("Converted: ", target.Foo);
+        }
+
+        [Fact]
+        public void MultiValueConverter_Should_Not_Skip_Valid_Null_ReferenceType_Value()
+        {
+            var target = new FuncMultiValueConverter<string, string>(v => string.Join(",", v.ToArray()));
+
+            object value = target.Convert(new[] { "Foo", "Bar", "Baz" }, typeof(string), null, CultureInfo.InvariantCulture);
+
+            Assert.Equal("Foo,Bar,Baz", value);
+
+            value = target.Convert(new[] { null, "Bar", "Baz" }, typeof(string), null, CultureInfo.InvariantCulture);
+
+            Assert.Equal(",Bar,Baz", value);
+        }
+
+        [Fact]
+        public void MultiValueConverter_Should_Not_Skip_Valid_Default_ValueType_Value()
+        {
+            var target = new FuncMultiValueConverter<StringValueTypeWrapper, string>(v => string.Join(",", v.ToArray()));
+
+            IList<object> create(string[] values) =>
+                values.Select(v => (object)(v != null ? new StringValueTypeWrapper() { Value = v } : default)).ToList();
+
+            object value = target.Convert(create(new[] { "Foo", "Bar", "Baz" }), typeof(string), null, CultureInfo.InvariantCulture);
+
+            Assert.Equal("Foo,Bar,Baz", value);
+
+            value = target.Convert(create(new[] { null, "Bar", "Baz" }), typeof(string), null, CultureInfo.InvariantCulture);
+
+            Assert.Equal(",Bar,Baz", value);
+        }
+
+        private struct StringValueTypeWrapper
+        {
+            public string Value;
+
+            public override string ToString() => Value;
+        }
+
+        private static IMultiValueConverter StringJoinConverter = new FuncMultiValueConverter<object, string>(v => string.Join(",", v.ToArray()));
+
+        private class Class1 : AvaloniaObject
+        {
+            public static readonly StyledProperty<string> FooProperty =
+                AvaloniaProperty.Register<Class1, string>("Foo");
+
+            public string Foo
+            {
+                get => GetValue(FooProperty);
+                set => SetValue(FooProperty, value);
+            }
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/DefaultValueConverterTests.cs b/tests/Avalonia.Base.UnitTests/Data/DefaultValueConverterTests.cs
index ecf559951a..f29dabb6bf 100644
--- a/tests/Avalonia.Base.UnitTests/Data/DefaultValueConverterTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/DefaultValueConverterTests.cs
@@ -50,6 +50,18 @@ namespace Avalonia.Base.UnitTests.Data.Converters
             Assert.Equal(TestEnum.Bar, result);
         }
 
+        [Fact]
+        public void Can_Convert_String_To_TimeSpan()
+        {
+            var result = DefaultValueConverter.Instance.Convert(
+                "00:00:10",
+                typeof(TimeSpan),
+                null,
+                CultureInfo.InvariantCulture);
+
+            Assert.Equal(TimeSpan.FromSeconds(10), result);
+        }
+
         [Fact]
         public void Can_Convert_Int_To_Enum()
         {
diff --git a/tests/Avalonia.Benchmarks/Avalonia.Benchmarks.csproj b/tests/Avalonia.Benchmarks/Avalonia.Benchmarks.csproj
index f503bf66a7..5fc3dce671 100644
--- a/tests/Avalonia.Benchmarks/Avalonia.Benchmarks.csproj
+++ b/tests/Avalonia.Benchmarks/Avalonia.Benchmarks.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <OutputType>Exe</OutputType>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
diff --git a/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj b/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
index 7fec6f2770..396dfee691 100644
--- a/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
+++ b/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <LangVersion>latest</LangVersion>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
diff --git a/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj b/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
index aa470bce9d..373b1bc82f 100644
--- a/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
+++ b/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <LangVersion>latest</LangVersion>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
diff --git a/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs b/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
index f44f89e91f..28e87dd671 100644
--- a/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
@@ -1,9 +1,5 @@
 using System;
-using System.Windows.Input;
-using Avalonia.Controls.Primitives;
-using Avalonia.Data;
 using Avalonia.Input;
-using Avalonia.Markup.Data;
 using Avalonia.Platform;
 using Avalonia.UnitTests;
 using Moq;
@@ -159,6 +155,19 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void Can_Set_Clear_ContextMenu_Property()
+        {
+            using (Application())
+            {
+                var target = new ContextMenu();
+                var control = new Panel();
+
+                control.ContextMenu = target;
+                control.ContextMenu = null;
+            }
+        }
+
         [Fact(Skip = "The only reason this test was 'passing' before was that the author forgot to call Window.ApplyTemplate()")]
         public void Cancelling_Closing_Leaves_ContextMenuOpen()
         {
@@ -200,16 +209,17 @@ namespace Avalonia.Controls.UnitTests
             screenImpl.Setup(x => x.ScreenCount).Returns(1);
             screenImpl.Setup(X => X.AllScreens).Returns( new[] { new Screen(1, screen, screen, true) });
 
-            popupImpl = MockWindowingPlatform.CreatePopupMock();
+            var windowImpl = MockWindowingPlatform.CreateWindowMock();
+            popupImpl = MockWindowingPlatform.CreatePopupMock(windowImpl.Object);
             popupImpl.SetupGet(x => x.Scaling).Returns(1);
+            windowImpl.Setup(x => x.CreatePopup()).Returns(popupImpl.Object);
 
-            var windowImpl = MockWindowingPlatform.CreateWindowMock(() => popupImpl.Object);
             windowImpl.Setup(x => x.Screen).Returns(screenImpl.Object);
 
             var services = TestServices.StyledWindow.With(
                                         inputManager: new InputManager(),
                                         windowImpl: windowImpl.Object,
-                                        windowingPlatform: new MockWindowingPlatform(() => windowImpl.Object, () => popupImpl.Object));
+                                        windowingPlatform: new MockWindowingPlatform(() => windowImpl.Object, x => popupImpl.Object));
 
             return UnitTestApplication.Start(services);
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupRootTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupRootTests.cs
index f75f6fcf91..d5ea111ee5 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupRootTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupRootTests.cs
@@ -5,11 +5,14 @@ using System;
 using System.Linq;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Primitives.PopupPositioning;
 using Avalonia.Controls.Templates;
 using Avalonia.LogicalTree;
+using Avalonia.Platform;
 using Avalonia.Styling;
 using Avalonia.UnitTests;
 using Avalonia.VisualTree;
+using Moq;
 using Xunit;
 
 namespace Avalonia.Controls.UnitTests.Primitives
@@ -175,9 +178,146 @@ namespace Avalonia.Controls.UnitTests.Primitives
             }
         }
 
-        private PopupRoot CreateTarget(TopLevel popupParent)
+        [Fact]
+        public void Child_Should_Be_Measured_With_Infinity()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new ChildControl();
+                var window = new Window();
+                var target = CreateTarget(window);
+                
+                target.Content = child;
+                target.Show();
+
+                Assert.Equal(Size.Infinity, child.MeasureSize);
+            }
+        }
+
+        [Fact]
+        public void Child_Should_Be_Measured_With_Width_Height_When_Set()
         {
-            var result = new PopupRoot(popupParent, popupParent.PlatformImpl.CreatePopup())
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new ChildControl();
+                var window = new Window();
+                var target = CreateTarget(window);
+
+                target.Width = 500;
+                target.Height = 600;
+                target.Content = child;
+                target.Show();
+
+                Assert.Equal(new Size(500, 600), child.MeasureSize);
+            }
+        }
+
+        [Fact]
+        public void Child_Should_Be_Measured_With_MaxWidth_MaxHeight_When_Set()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new ChildControl();
+                var window = new Window();
+                var target = CreateTarget(window);
+
+                target.MaxWidth = 500;
+                target.MaxHeight = 600;
+                target.Content = child;
+                target.Show();
+
+                Assert.Equal(new Size(500, 600), child.MeasureSize);
+            }
+        }
+
+        [Fact]
+        public void Should_Not_Have_Offset_On_Bounds_When_Content_Larger_Than_Max_Window_Size()
+        {
+            // Issue #3784.
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var window = new Window();
+                var popupImpl = MockWindowingPlatform.CreatePopupMock(window.PlatformImpl);
+
+                var child = new Canvas
+                {
+                    Width = 400,
+                    Height = 1344,
+                };
+
+                var target = CreateTarget(window, popupImpl.Object);
+                target.Content = child;
+
+                target.Show();
+
+                Assert.Equal(new Size(400, 1024), target.Bounds.Size);
+
+                // Issue #3784 causes this to be (0, 160) which makes no sense as Window has no
+                // parent control to be offset against.
+                Assert.Equal(new Point(0, 0), target.Bounds.Position);
+            }
+        }
+
+        [Fact]
+        public void MinWidth_MinHeight_Should_Be_Respected()
+        {
+            // Issue #3796
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var window = new Window();
+                var popupImpl = MockWindowingPlatform.CreatePopupMock(window.PlatformImpl);
+
+                var target = CreateTarget(window, popupImpl.Object);
+                target.MinWidth = 400;
+                target.MinHeight = 800;
+                target.Content = new Border
+                {
+                    Width = 100,
+                    Height = 100,
+                };
+
+                target.Show();
+
+                Assert.Equal(new Rect(0, 0, 400, 800), target.Bounds);
+                Assert.Equal(new Size(400, 800), target.ClientSize);
+                Assert.Equal(new Size(400, 800), target.PlatformImpl.ClientSize);
+            }
+        }
+
+        [Fact]
+        public void Setting_Width_Should_Resize_WindowImpl()
+        {
+            // Issue #3796
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var window = new Window();
+                var popupImpl = MockWindowingPlatform.CreatePopupMock(window.PlatformImpl);
+                var positioner = new Mock<IPopupPositioner>();
+                popupImpl.Setup(x => x.PopupPositioner).Returns(positioner.Object);
+
+                var target = CreateTarget(window, popupImpl.Object);
+                target.Width = 400;
+                target.Height = 800;
+
+                target.Show();
+
+                Assert.Equal(400, target.Width);
+                Assert.Equal(800, target.Height);
+
+                target.Width = 410;
+                target.LayoutManager.ExecuteLayoutPass();
+
+                positioner.Verify(x => 
+                    x.Update(It.Is<PopupPositionerParameters>(x => x.Size.Width == 410)));
+                Assert.Equal(410, target.Width);
+            }
+        }
+
+        private PopupRoot CreateTarget(TopLevel popupParent, IPopupImpl impl = null)
+        {
+            impl ??= popupParent.PlatformImpl.CreatePopup();
+
+            var result = new PopupRoot(popupParent, impl)
             {
                 Template = new FuncControlTemplate<PopupRoot>((parent, scope) =>
                     new ContentPresenter
@@ -220,5 +360,16 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Popup = (Popup)this.GetVisualChildren().Single();
             }
         }
+
+        private class ChildControl : Control
+        {
+            public Size MeasureSize { get; private set; }
+
+            protected override Size MeasureOverride(Size availableSize)
+            {
+                MeasureSize = availableSize;
+                return base.MeasureOverride(availableSize);
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
index 7cb9fccee8..5ec5c2b2f9 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
@@ -332,11 +332,11 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             return UnitTestApplication.Start(TestServices.StyledWindow.With(windowingPlatform:
                 new MockWindowingPlatform(null,
-                    () =>
+                    x =>
                     {
                         if(UsePopupHost)
                             return null;
-                        return MockWindowingPlatform.CreatePopupMock().Object;
+                        return MockWindowingPlatform.CreatePopupMock(x).Object;
                     })));
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 696c0dbf46..004cf009fc 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -1202,6 +1202,28 @@ namespace Avalonia.Controls.UnitTests.Primitives
             target.MoveSelection(NavigationDirection.Next, true);
         }
 
+        [Fact]
+        public void MoveSelection_Does_Select_Disabled_Controls()
+        {
+            // Issue #3426.
+            var target = new TestSelector
+            {
+                Template = Template(),
+                Items = new[]
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem { IsEnabled = false },
+                },
+                SelectedIndex = 0,
+            };
+
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+            target.MoveSelection(NavigationDirection.Next, true);
+
+            Assert.Equal(0, target.SelectedIndex);
+        }
+
         [Fact]
         public void Pre_Selecting_Item_Should_Set_Selection_After_It_Was_Added_When_AlwaysSelected()
         {
diff --git a/tests/Avalonia.Controls.UnitTests/WindowTests.cs b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
index 0508edd92f..b431ac5b48 100644
--- a/tests/Avalonia.Controls.UnitTests/WindowTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
@@ -7,6 +7,7 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Avalonia.Layout;
 using Avalonia.Platform;
 using Avalonia.Rendering;
 using Avalonia.UnitTests;
@@ -341,11 +342,229 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void Child_Should_Be_Measured_With_Width_And_Height_If_SizeToContent_Is_Manual()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new ChildControl();
+                var target = new Window 
+                { 
+                    Width = 100,
+                    Height = 50,
+                    SizeToContent = SizeToContent.Manual,
+                    Content = child 
+                };
+
+                target.Show();
+
+                Assert.Equal(1, child.MeasureSizes.Count);
+                Assert.Equal(new Size(100, 50), child.MeasureSizes[0]);
+            }
+        }
+
+        [Fact]
+        public void Child_Should_Be_Measured_With_ClientSize_If_SizeToContent_Is_Manual_And_No_Width_Height_Specified()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var windowImpl = MockWindowingPlatform.CreateWindowMock();
+                windowImpl.Setup(x => x.ClientSize).Returns(new Size(550, 450));
+
+                var child = new ChildControl();
+                var target = new Window(windowImpl.Object)
+                {
+                    SizeToContent = SizeToContent.Manual,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(1, child.MeasureSizes.Count);
+                Assert.Equal(new Size(550, 450), child.MeasureSizes[0]);
+            }
+        }
+
+        [Fact]
+        public void Child_Should_Be_Measured_With_Infinity_If_SizeToContent_Is_WidthAndHeight()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new ChildControl();
+                var target = new Window
+                {
+                    Width = 100,
+                    Height = 50,
+                    SizeToContent = SizeToContent.WidthAndHeight,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(1, child.MeasureSizes.Count);
+                Assert.Equal(Size.Infinity, child.MeasureSizes[0]);
+            }
+        }
+
+        [Fact]
+        public void Should_Not_Have_Offset_On_Bounds_When_Content_Larger_Than_Max_Window_Size()
+        {
+            // Issue #3784.
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var windowImpl = MockWindowingPlatform.CreateWindowMock();
+                var clientSize = new Size(200, 200);
+                var maxClientSize = new Size(480, 480);
+
+                windowImpl.Setup(x => x.Resize(It.IsAny<Size>())).Callback<Size>(size =>
+                {
+                    clientSize = size.Constrain(maxClientSize);
+                    windowImpl.Object.Resized?.Invoke(clientSize);
+                });
+
+                windowImpl.Setup(x => x.ClientSize).Returns(() => clientSize);
+
+                var child = new Canvas
+                {
+                    Width = 400,
+                    Height = 800,
+                };
+                var target = new Window(windowImpl.Object)
+                {
+                    SizeToContent = SizeToContent.WidthAndHeight,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(new Size(400, 480), target.Bounds.Size);
+
+                // Issue #3784 causes this to be (0, 160) which makes no sense as Window has no
+                // parent control to be offset against.
+                Assert.Equal(new Point(0, 0), target.Bounds.Position);
+            }
+        }
+
+        [Fact]
+        public void Width_Height_Should_Not_Be_NaN_After_Show_With_SizeToContent_WidthAndHeight()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new Canvas
+                {
+                    Width = 400,
+                    Height = 800,
+                };
+
+                var target = new Window()
+                {
+                    SizeToContent = SizeToContent.WidthAndHeight,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(400, target.Width);
+                Assert.Equal(800, target.Height);
+            }
+        }
+
+        [Fact]
+        public void SizeToContent_Should_Not_Be_Lost_On_Show()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new Canvas
+                {
+                    Width = 400,
+                    Height = 800,
+                };
+
+                var target = new Window()
+                {
+                    SizeToContent = SizeToContent.WidthAndHeight,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(SizeToContent.WidthAndHeight, target.SizeToContent);
+            }
+        }
+
+        [Fact]
+        public void Width_Height_Should_Be_Updated_When_SizeToContent_Is_WidthAndHeight()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var child = new Canvas
+                {
+                    Width = 400,
+                    Height = 800,
+                };
+
+                var target = new Window()
+                {
+                    SizeToContent = SizeToContent.WidthAndHeight,
+                    Content = child
+                };
+
+                target.Show();
+
+                Assert.Equal(400, target.Width);
+                Assert.Equal(800, target.Height);
+
+                child.Width = 410;
+                target.LayoutManager.ExecuteLayoutPass();
+
+                Assert.Equal(410, target.Width);
+                Assert.Equal(800, target.Height);
+                Assert.Equal(SizeToContent.WidthAndHeight, target.SizeToContent);
+            }
+        }
+
+        [Fact]
+        public void Setting_Width_Should_Resize_WindowImpl()
+        {
+            // Issue #3796
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var target = new Window()
+                {
+                    Width = 400,
+                    Height = 800,
+                };
+
+                target.Show();
+
+                Assert.Equal(400, target.Width);
+                Assert.Equal(800, target.Height);
+
+                target.Width = 410;
+                target.LayoutManager.ExecuteLayoutPass();
+
+                var windowImpl = Mock.Get(target.PlatformImpl);
+                windowImpl.Verify(x => x.Resize(new Size(410, 800)));
+                Assert.Equal(410, target.Width);
+            }
+        }
+
         private IWindowImpl CreateImpl(Mock<IRenderer> renderer)
         {
             return Mock.Of<IWindowImpl>(x =>
                 x.Scaling == 1 &&
                 x.CreateRenderer(It.IsAny<IRenderRoot>()) == renderer.Object);
         }
+
+        private class ChildControl : Control
+        {
+            public List<Size> MeasureSizes { get; } = new List<Size>();
+
+            protected override Size MeasureOverride(Size availableSize)
+            {
+                MeasureSizes.Add(availableSize);
+                return base.MeasureOverride(availableSize);
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.DesignerSupport.TestApp/Avalonia.DesignerSupport.TestApp.csproj b/tests/Avalonia.DesignerSupport.TestApp/Avalonia.DesignerSupport.TestApp.csproj
index 6bba5e7348..73a1d586b5 100644
--- a/tests/Avalonia.DesignerSupport.TestApp/Avalonia.DesignerSupport.TestApp.csproj
+++ b/tests/Avalonia.DesignerSupport.TestApp/Avalonia.DesignerSupport.TestApp.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>
diff --git a/tests/Avalonia.DesignerSupport.Tests/Avalonia.DesignerSupport.Tests.csproj b/tests/Avalonia.DesignerSupport.Tests/Avalonia.DesignerSupport.Tests.csproj
index 94c2ed934d..dad500e3c6 100644
--- a/tests/Avalonia.DesignerSupport.Tests/Avalonia.DesignerSupport.Tests.csproj
+++ b/tests/Avalonia.DesignerSupport.Tests/Avalonia.DesignerSupport.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
     <OutputType>Library</OutputType>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
diff --git a/tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs b/tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs
index 01fa0e7783..dd704bc775 100644
--- a/tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs
+++ b/tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs
@@ -28,12 +28,12 @@ namespace Avalonia.DesignerSupport.Tests
 
         [SkippableTheory,
          InlineData(
-            @"..\..\..\..\..\tests/Avalonia.DesignerSupport.TestApp/bin/$BUILD/netcoreapp2.0/",
+            @"..\..\..\..\..\tests/Avalonia.DesignerSupport.TestApp/bin/$BUILD/netcoreapp3.1/",
             "Avalonia.DesignerSupport.TestApp",
             "Avalonia.DesignerSupport.TestApp.dll",
             @"..\..\..\..\..\tests\Avalonia.DesignerSupport.TestApp\MainWindow.xaml"),
          InlineData(
-            @"..\..\..\..\..\samples\ControlCatalog.NetCore\bin\$BUILD\netcoreapp2.0\",
+            @"..\..\..\..\..\samples\ControlCatalog.NetCore\bin\$BUILD\netcoreapp3.1\",
             "ControlCatalog.NetCore",
             "ControlCatalog.dll",
             @"..\..\..\..\..\samples\ControlCatalog\MainWindow.xaml")]
diff --git a/tests/Avalonia.Direct2D1.RenderTests/Avalonia.Direct2D1.RenderTests.csproj b/tests/Avalonia.Direct2D1.RenderTests/Avalonia.Direct2D1.RenderTests.csproj
index ecc928461e..0378acad05 100644
--- a/tests/Avalonia.Direct2D1.RenderTests/Avalonia.Direct2D1.RenderTests.csproj
+++ b/tests/Avalonia.Direct2D1.RenderTests/Avalonia.Direct2D1.RenderTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\Avalonia.RenderTests\**\*.cs" />
diff --git a/tests/Avalonia.Direct2D1.UnitTests/Avalonia.Direct2D1.UnitTests.csproj b/tests/Avalonia.Direct2D1.UnitTests/Avalonia.Direct2D1.UnitTests.csproj
index b09902332b..079cc49c2e 100644
--- a/tests/Avalonia.Direct2D1.UnitTests/Avalonia.Direct2D1.UnitTests.csproj
+++ b/tests/Avalonia.Direct2D1.UnitTests/Avalonia.Direct2D1.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\Moq.props" />
diff --git a/tests/Avalonia.Input.UnitTests/Avalonia.Input.UnitTests.csproj b/tests/Avalonia.Input.UnitTests/Avalonia.Input.UnitTests.csproj
index ef515ce155..dd50eff2b6 100644
--- a/tests/Avalonia.Input.UnitTests/Avalonia.Input.UnitTests.csproj
+++ b/tests/Avalonia.Input.UnitTests/Avalonia.Input.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Interactivity.UnitTests/Avalonia.Interactivity.UnitTests.csproj b/tests/Avalonia.Interactivity.UnitTests/Avalonia.Interactivity.UnitTests.csproj
index 2bde78ad63..a9f5318e8f 100644
--- a/tests/Avalonia.Interactivity.UnitTests/Avalonia.Interactivity.UnitTests.csproj
+++ b/tests/Avalonia.Interactivity.UnitTests/Avalonia.Interactivity.UnitTests.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
     <LangVersion>latest</LangVersion>
diff --git a/tests/Avalonia.Layout.UnitTests/Avalonia.Layout.UnitTests.csproj b/tests/Avalonia.Layout.UnitTests/Avalonia.Layout.UnitTests.csproj
index 63f7f3ec0e..463bc50008 100644
--- a/tests/Avalonia.Layout.UnitTests/Avalonia.Layout.UnitTests.csproj
+++ b/tests/Avalonia.Layout.UnitTests/Avalonia.Layout.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
     <OutputType>Library</OutputType>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
diff --git a/tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs b/tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs
index 6cf38b6121..dcc29a9716 100644
--- a/tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs
+++ b/tests/Avalonia.Layout.UnitTests/FullLayoutTests.cs
@@ -1,28 +1,12 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
-// Licensed under the MIT license. See licence.md file in the project root for full license information.
-
-using System.Diagnostics;
-using System.IO;
 using System.Linq;
-using Moq;
 using Avalonia.Controls;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
-using Avalonia.Diagnostics;
-using Avalonia.Input;
-using Avalonia.Platform;
-using Avalonia.Rendering;
-using Avalonia.Shared.PlatformSupport;
 using Avalonia.Styling;
-using Avalonia.Themes.Default;
+using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using Xunit;
-using Avalonia.Media;
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.UnitTests;
-using Avalonia.UnitTests;
 
 namespace Avalonia.Layout.UnitTests
 {
@@ -31,10 +15,8 @@ namespace Avalonia.Layout.UnitTests
         [Fact]
         public void Grandchild_Size_Changed()
         {
-            using (var context = AvaloniaLocator.EnterScope())
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                RegisterServices();
-
                 Border border;
                 TextBlock textBlock;
 
@@ -58,7 +40,6 @@ namespace Avalonia.Layout.UnitTests
                 };
 
                 window.Show();
-                window.LayoutManager.ExecuteInitialLayoutPass(window);
 
                 Assert.Equal(new Size(400, 400), border.Bounds.Size);
                 textBlock.Width = 200;
@@ -71,10 +52,8 @@ namespace Avalonia.Layout.UnitTests
         [Fact]
         public void Test_ScrollViewer_With_TextBlock()
         {
-            using (var context = AvaloniaLocator.EnterScope())
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                RegisterServices();
-
                 ScrollViewer scrollViewer;
                 TextBlock textBlock;
 
@@ -82,7 +61,6 @@ namespace Avalonia.Layout.UnitTests
                 {
                     Width = 800,
                     Height = 600,
-                    SizeToContent = SizeToContent.WidthAndHeight,
                     Content = scrollViewer = new ScrollViewer
                     {
                         Width = 200,
@@ -102,7 +80,6 @@ namespace Avalonia.Layout.UnitTests
                 window.Resources["ScrollBarThickness"] = 10.0;
 
                 window.Show();
-                window.LayoutManager.ExecuteInitialLayoutPass(window);
 
                 Assert.Equal(new Size(800, 600), window.Bounds.Size);
                 Assert.Equal(new Size(200, 200), scrollViewer.Bounds.Size);
@@ -134,84 +111,5 @@ namespace Avalonia.Layout.UnitTests
         {
             return v.Bounds.Position;
         }
-
-        class FormattedTextMock : IFormattedTextImpl
-        {
-            public FormattedTextMock(string text)
-            {
-                Text = text;
-            }
-
-            public Size Constraint { get; set; }
-
-            public string Text { get; }
-
-            public Rect Bounds => Rect.Empty;
-
-            public void Dispose()
-            {
-            }
-
-            public IEnumerable<FormattedTextLine> GetLines() => new FormattedTextLine[0];
-
-            public TextHitTestResult HitTestPoint(Point point) => new TextHitTestResult();
-
-            public Rect HitTestTextPosition(int index) => new Rect();
-
-            public IEnumerable<Rect> HitTestTextRange(int index, int length) => new Rect[0];
-
-            public Size Measure() => Constraint;
-        }
-
-        private void RegisterServices()
-        {
-            var globalStyles = new Mock<IGlobalStyles>();
-            var globalStylesResources = globalStyles.As<IResourceNode>();
-            var outObj = (object)10;
-            globalStylesResources.Setup(x => x.TryGetResource("FontSizeNormal", out outObj)).Returns(true);
-
-            var renderInterface = new Mock<IPlatformRenderInterface>();
-            renderInterface.Setup(x =>
-                x.CreateFormattedText(
-                    It.IsAny<string>(),
-                    It.IsAny<Typeface>(),
-                    It.IsAny<TextAlignment>(),
-                    It.IsAny<TextWrapping>(),
-                    It.IsAny<Size>(),
-                    It.IsAny<IReadOnlyList<FormattedTextStyleSpan>>()))
-                .Returns(new FormattedTextMock("TEST"));
-
-            var streamGeometry = new Mock<IStreamGeometryImpl>();
-            streamGeometry.Setup(x =>
-                    x.Open())
-                .Returns(new Mock<IStreamGeometryContextImpl>().Object);
-
-            renderInterface.Setup(x =>
-                    x.CreateStreamGeometry())
-                .Returns(streamGeometry.Object);
-
-            var windowImpl = new Mock<IWindowImpl>();
-
-            Size clientSize = default(Size);
-
-            windowImpl.SetupGet(x => x.ClientSize).Returns(() => clientSize);
-            windowImpl.Setup(x => x.Resize(It.IsAny<Size>())).Callback<Size>(s => clientSize = s);
-            windowImpl.Setup(x => x.MaxClientSize).Returns(new Size(1024, 1024));
-            windowImpl.SetupGet(x => x.Scaling).Returns(1);
-
-            AvaloniaLocator.CurrentMutable
-                .Bind<IStandardCursorFactory>().ToConstant(new CursorFactoryMock())
-                .Bind<IAssetLoader>().ToConstant(new AssetLoader())
-                .Bind<IInputManager>().ToConstant(new Mock<IInputManager>().Object)
-                .Bind<IGlobalStyles>().ToConstant(globalStyles.Object)
-                .Bind<IRuntimePlatform>().ToConstant(new AppBuilder().RuntimePlatform)
-                .Bind<IPlatformRenderInterface>().ToConstant(renderInterface.Object)
-                .Bind<IStyler>().ToConstant(new Styler())
-                .Bind<IWindowingPlatform>().ToConstant(new Avalonia.Controls.UnitTests.WindowingPlatformMock(() => windowImpl.Object));
-
-            var theme = new DefaultTheme();
-            globalStyles.Setup(x => x.IsStylesInitialized).Returns(true);
-            globalStyles.Setup(x => x.Styles).Returns(theme);
-        }
     }
 }
diff --git a/tests/Avalonia.Layout.UnitTests/LayoutManagerTests.cs b/tests/Avalonia.Layout.UnitTests/LayoutManagerTests.cs
index 3f20c9a76a..0165b91844 100644
--- a/tests/Avalonia.Layout.UnitTests/LayoutManagerTests.cs
+++ b/tests/Avalonia.Layout.UnitTests/LayoutManagerTests.cs
@@ -374,5 +374,38 @@ namespace Avalonia.Layout.UnitTests
             Assert.True(control.Measured);
             Assert.True(control.IsMeasureValid);
         }
+
+        [Fact]
+        public void Calling_ExecuteLayoutPass_From_ExecuteInitialLayoutPass_Does_Not_Break_Measure()
+        {
+            // Test for issue #3550.
+            var control = new LayoutTestControl();
+            var root = new LayoutTestRoot { Child = control };
+            var count = 0;
+
+            root.LayoutManager.ExecuteInitialLayoutPass(root);
+            control.Measured = false;
+
+            control.DoMeasureOverride = (l, s) =>
+            {
+                if (count++ == 0)
+                {
+                    control.InvalidateMeasure();
+                    root.LayoutManager.ExecuteLayoutPass();
+                    return new Size(100, 100);
+                }
+                else
+                {
+                    return new Size(200, 200);
+                }
+            };
+
+            root.InvalidateMeasure();
+            control.InvalidateMeasure();
+            root.LayoutManager.ExecuteInitialLayoutPass(root);
+
+            Assert.Equal(new Size(200, 200), control.Bounds.Size);
+            Assert.Equal(new Size(200, 200), control.DesiredSize);
+        }
     }
 }
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index 1da4746516..6aca8f7d4e 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -4,12 +4,16 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.Remoting.Contexts;
 using Avalonia.Controls;
 using Avalonia.Controls.Templates;
 using Avalonia.Diagnostics;
+using Avalonia.Input;
 using Avalonia.Layout;
+using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Rendering;
+using Avalonia.Styling;
 using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using JetBrains.dotMemoryUnit;
@@ -370,9 +374,133 @@ namespace Avalonia.LeakTests
             }
         }
 
+        [Fact]
+        public void Control_With_Style_RenderTransform_Is_Freed()
+        {
+            // # Issue #3545
+            using (Start())
+            {
+                Func<Window> run = () =>
+                {
+                    var window = new Window
+                    {
+                        Styles =
+                        {
+                            new Style(x => x.OfType<Canvas>())
+                            {
+                                Setters =
+                                {
+                                    new Setter
+                                    {
+                                        Property = Visual.RenderTransformProperty,
+                                        Value = new RotateTransform(45),
+                                    }
+                                }
+                            }
+                        },
+                        Content = new Canvas()
+                    };
+
+                    window.Show();
+
+                    // Do a layout and make sure that Canvas gets added to visual tree with
+                    // its render transform.
+                    window.LayoutManager.ExecuteInitialLayoutPass(window);
+                    var canvas = Assert.IsType<Canvas>(window.Presenter.Child);
+                    Assert.IsType<RotateTransform>(canvas.RenderTransform);
+
+                    // Clear the content and ensure the Canvas is removed.
+                    window.Content = null;
+                    window.LayoutManager.ExecuteLayoutPass();
+                    Assert.Null(window.Presenter.Child);
+
+                    return window;
+                };
+
+                var result = run();
+
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<Canvas>()).ObjectsCount));
+            }
+        }
+
+        [Fact]
+        public void Attached_ContextMenu_Is_Freed()
+        {
+            using (Start())
+            {
+                void AttachShowAndDetachContextMenu(Control control)
+                {
+                    var contextMenu = new ContextMenu
+                    {
+                        Items = new[]
+                        {
+                            new MenuItem { Header = "Foo" },
+                            new MenuItem { Header = "Foo" },
+                        }
+                    };
+
+                    control.ContextMenu = contextMenu;
+                    contextMenu.Open(control);
+                    contextMenu.Close();
+                    control.ContextMenu = null;
+                }
+
+                var window = new Window();
+                window.Show();
+
+                Assert.Same(window, FocusManager.Instance.Current);
+
+                AttachShowAndDetachContextMenu(window);
+
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<ContextMenu>()).ObjectsCount));
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<MenuItem>()).ObjectsCount));
+            }
+        }
+
+        [Fact]
+        public void Standalone_ContextMenu_Is_Freed()
+        {
+            using (Start())
+            {
+                void BuildAndShowContextMenu(Control control)
+                {
+                    var contextMenu = new ContextMenu
+                    {
+                        Items = new[]
+                        {
+                            new MenuItem { Header = "Foo" },
+                            new MenuItem { Header = "Foo" },
+                        }
+                    };
+
+                    contextMenu.Open(control);
+                    contextMenu.Close();
+                }
+
+                var window = new Window();
+                window.Show();
+
+                Assert.Same(window, FocusManager.Instance.Current);
+
+                BuildAndShowContextMenu(window);
+                BuildAndShowContextMenu(window);
+
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<ContextMenu>()).ObjectsCount));
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<MenuItem>()).ObjectsCount));
+            }
+        }
+
         private IDisposable Start()
         {
-            return UnitTestApplication.Start(TestServices.StyledWindow);
+            return UnitTestApplication.Start(TestServices.StyledWindow.With(
+                focusManager: new FocusManager(),
+                keyboardDevice: () => new KeyboardDevice(),
+                inputManager: new InputManager()));
         }
 
         private class Node
diff --git a/tests/Avalonia.Markup.UnitTests/Avalonia.Markup.UnitTests.csproj b/tests/Avalonia.Markup.UnitTests/Avalonia.Markup.UnitTests.csproj
index aba5f2d469..ec5b2f0ed1 100644
--- a/tests/Avalonia.Markup.UnitTests/Avalonia.Markup.UnitTests.csproj
+++ b/tests/Avalonia.Markup.UnitTests/Avalonia.Markup.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj b/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
index 3107f4cf22..e8c4daa7bc 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index f7629e5b9e..96a0789f3c 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -278,5 +278,67 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 Assert.Equal(Colors.Red, ((ISolidColorBrush)notFoo.Background).Color);
             }
         }
+
+        [Fact]
+        public void Style_Can_Use_Or_Selector_1()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <Style Selector='Border.foo, Border.bar'>
+            <Setter Property='Background' Value='Red'/>
+        </Style>
+    </Window.Styles>
+    <StackPanel>
+        <Border Name='foo' Classes='foo'/>
+        <Border Name='bar' Classes='bar'/>
+        <Border Name='baz' Classes='baz'/>
+    </StackPanel>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var foo = window.FindControl<Border>("foo");
+                var bar = window.FindControl<Border>("bar");
+                var baz = window.FindControl<Border>("baz");
+
+                Assert.Equal(Brushes.Red, foo.Background);
+                Assert.Equal(Brushes.Red, bar.Background);
+                Assert.Null(baz.Background);
+            }
+        }
+
+        [Fact]
+        public void Style_Can_Use_Or_Selector_2()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <Style Selector='Button,Carousel,ListBox'>
+            <Setter Property='Background' Value='Red'/>
+        </Style>
+    </Window.Styles>
+    <StackPanel>
+        <Button Name='button'/>
+        <Carousel Name='carousel'/>
+        <ListBox Name='listBox'/>
+    </StackPanel>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+                var carousel = window.FindControl<Carousel>("carousel");
+                var listBox = window.FindControl<ListBox>("listBox");
+
+                Assert.Equal(Brushes.Red, button.Background);
+                Assert.Equal(Brushes.Red, carousel.Background);
+                Assert.Equal(Brushes.Red, listBox.Background);
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.ReactiveUI.UnitTests/Avalonia.ReactiveUI.UnitTests.csproj b/tests/Avalonia.ReactiveUI.UnitTests/Avalonia.ReactiveUI.UnitTests.csproj
index 7c0ff79183..32dc498781 100644
--- a/tests/Avalonia.ReactiveUI.UnitTests/Avalonia.ReactiveUI.UnitTests.csproj
+++ b/tests/Avalonia.ReactiveUI.UnitTests/Avalonia.ReactiveUI.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\Moq.props" />
diff --git a/tests/Avalonia.Skia.RenderTests/Avalonia.Skia.RenderTests.csproj b/tests/Avalonia.Skia.RenderTests/Avalonia.Skia.RenderTests.csproj
index a9452b4def..9178e94d0d 100644
--- a/tests/Avalonia.Skia.RenderTests/Avalonia.Skia.RenderTests.csproj
+++ b/tests/Avalonia.Skia.RenderTests/Avalonia.Skia.RenderTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
     <DefineConstants>AVALONIA_SKIA;AVALONIA_SKIA_SKIP_FAIL</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
diff --git a/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj b/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
index 0473355fcd..e38a752ff9 100644
--- a/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
+++ b/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\Moq.props" />
diff --git a/tests/Avalonia.Styling.UnitTests/Avalonia.Styling.UnitTests.csproj b/tests/Avalonia.Styling.UnitTests/Avalonia.Styling.UnitTests.csproj
index 3fd280f7ab..2b7f6263a7 100644
--- a/tests/Avalonia.Styling.UnitTests/Avalonia.Styling.UnitTests.csproj
+++ b/tests/Avalonia.Styling.UnitTests/Avalonia.Styling.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <NoWarn>CS0067</NoWarn>
     <IsTestProject>true</IsTestProject>
diff --git a/tests/Avalonia.UnitTests/MockWindowingPlatform.cs b/tests/Avalonia.UnitTests/MockWindowingPlatform.cs
index a6701ef655..b3e4b4edbc 100644
--- a/tests/Avalonia.UnitTests/MockWindowingPlatform.cs
+++ b/tests/Avalonia.UnitTests/MockWindowingPlatform.cs
@@ -8,61 +8,122 @@ namespace Avalonia.UnitTests
 {
     public class MockWindowingPlatform : IWindowingPlatform
     {
+        private static readonly Size s_screenSize = new Size(1280, 1024);
         private readonly Func<IWindowImpl> _windowImpl;
-        private readonly Func<IPopupImpl> _popupImpl;
+        private readonly Func<IWindowBaseImpl, IPopupImpl> _popupImpl;
 
-        public MockWindowingPlatform(Func<IWindowImpl> windowImpl = null, Func<IPopupImpl> popupImpl = null )
+        public MockWindowingPlatform(
+            Func<IWindowImpl> windowImpl = null,
+            Func<IWindowBaseImpl, IPopupImpl> popupImpl = null )
         {
             _windowImpl = windowImpl;
             _popupImpl = popupImpl;
         }
 
-        public static Mock<IWindowImpl> CreateWindowMock(Func<IPopupImpl> popupImpl = null)
+        public static Mock<IWindowImpl> CreateWindowMock()
         {
-            var win = Mock.Of<IWindowImpl>(x => x.Scaling == 1);
-            var mock = Mock.Get(win);
-            mock.Setup(x => x.CreatePopup()).Returns(() =>
+            var windowImpl = new Mock<IWindowImpl>();
+            var position = new PixelPoint();
+            var clientSize = new Size(800, 600);
+
+            windowImpl.SetupAllProperties();
+            windowImpl.Setup(x => x.ClientSize).Returns(() => clientSize);
+            windowImpl.Setup(x => x.Scaling).Returns(1);
+            windowImpl.Setup(x => x.Screen).Returns(CreateScreenMock().Object);
+            windowImpl.Setup(x => x.Position).Returns(() => position);
+            SetupToplevel(windowImpl);
+
+            windowImpl.Setup(x => x.CreatePopup()).Returns(() =>
+            {
+                return CreatePopupMock(windowImpl.Object).Object;
+            });
+
+            windowImpl.Setup(x => x.Dispose()).Callback(() =>
             {
-                if (popupImpl != null)
-                    return popupImpl();
-                return CreatePopupMock().Object;
+                windowImpl.Object.Closed?.Invoke();
+            });
 
+            windowImpl.Setup(x => x.Move(It.IsAny<PixelPoint>())).Callback<PixelPoint>(x =>
+            {
+                position = x;
+                windowImpl.Object.PositionChanged?.Invoke(x);
             });
-            mock.Setup(x => x.Dispose()).Callback(() =>
+
+            windowImpl.Setup(x => x.Resize(It.IsAny<Size>())).Callback<Size>(x =>
             {
-                mock.Object.Closed?.Invoke();
+                clientSize = x.Constrain(s_screenSize);
+                windowImpl.Object.Resized?.Invoke(clientSize);
             });
-            PixelPoint pos = default;
-            mock.SetupGet(x => x.Position).Returns(() => pos);
-            mock.Setup(x => x.Move(It.IsAny<PixelPoint>())).Callback(new Action<PixelPoint>(np => pos = np));
-            SetupToplevel(mock);
-            return mock;
+
+            windowImpl.Setup(x => x.Show()).Callback(() =>
+            {
+                windowImpl.Object.Activated?.Invoke();
+            });
+
+            return windowImpl;
         }
 
-        static void SetupToplevel<T>(Mock<T> mock) where T : class, ITopLevelImpl
+        public static Mock<IPopupImpl> CreatePopupMock(IWindowBaseImpl parent)
         {
-            mock.SetupGet(x => x.MouseDevice).Returns(new MouseDevice());
+            var popupImpl = new Mock<IPopupImpl>();
+            var clientSize = new Size();
+
+            var positionerHelper = new ManagedPopupPositionerPopupImplHelper(parent, (pos, size, scale) =>
+            {
+                clientSize = size.Constrain(s_screenSize);
+                popupImpl.Object.PositionChanged?.Invoke(pos);
+                popupImpl.Object.Resized?.Invoke(clientSize);
+            });
+            
+            var positioner = new ManagedPopupPositioner(positionerHelper);
+
+            popupImpl.SetupAllProperties();
+            popupImpl.Setup(x => x.ClientSize).Returns(() => clientSize);
+            popupImpl.Setup(x => x.Scaling).Returns(1);
+            popupImpl.Setup(x => x.PopupPositioner).Returns(positioner);
+            
+            SetupToplevel(popupImpl);
+            
+            return popupImpl;
         }
 
-        public static Mock<IPopupImpl> CreatePopupMock()
+        public static Mock<IScreenImpl> CreateScreenMock()
         {
-            var positioner = Mock.Of<IPopupPositioner>();
-            var popup = Mock.Of<IPopupImpl>(x => x.Scaling == 1);
-            var mock = Mock.Get(popup);
-            mock.SetupGet(x => x.PopupPositioner).Returns(positioner);
-            SetupToplevel(mock);
-            
-            return mock;
+            var screenImpl = new Mock<IScreenImpl>();
+            var bounds = new PixelRect(0, 0, (int)s_screenSize.Width, (int)s_screenSize.Height);
+            var screen = new Screen(96, bounds, bounds, true);
+            screenImpl.Setup(x => x.AllScreens).Returns(new[] { screen });
+            screenImpl.Setup(x => x.ScreenCount).Returns(1);
+            return screenImpl;
         }
 
         public IWindowImpl CreateWindow()
         {
-            return _windowImpl?.Invoke() ?? CreateWindowMock(_popupImpl).Object;
+            if (_windowImpl is object)
+            {
+                return _windowImpl();
+            }
+            else
+            {
+                var mock = CreateWindowMock();
+
+                if (_popupImpl is object)
+                {
+                    mock.Setup(x => x.CreatePopup()).Returns(() => _popupImpl(mock.Object));
+                }
+
+                return mock.Object;
+            }
         }
 
         public IEmbeddableWindowImpl CreateEmbeddableWindow()
         {
             throw new NotImplementedException();
         }
+
+        private static void SetupToplevel<T>(Mock<T> mock) where T : class, ITopLevelImpl
+        {
+            mock.SetupGet(x => x.MouseDevice).Returns(new MouseDevice());
+        }
     }
 }
diff --git a/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj b/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
index 50c2e580b0..2828edc20d 100644
--- a/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
+++ b/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.0;net47</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>