Application is now always the root of the parent stack

src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.cs

@@ -73,6 +73,10 @@ namespace Avalonia.Build.Tasks
                 asm.MainModule.ImportReference(editorBrowsableAttribute.GetConstructors()
                     .First(c => c.Parameters.Count == 1));
 
+            var runtimeHelpers = typeSystem.GetType("Avalonia.Markup.Xaml.XamlIl.Runtime.XamlIlRuntimeHelpers");
+            var getRootServiceProvider = asm.MainModule.ImportReference(
+                typeSystem.GetTypeReference(runtimeHelpers).Resolve().Methods
+                    .First(x => x.Name == "GetRootServiceProviderV1"));
             
             var loaderDispatcherDef = new TypeDefinition("CompiledAvaloniaXaml", "!XamlLoader",
                 TypeAttributes.Class, asm.MainModule.TypeSystem.Object);
@@ -158,7 +162,7 @@ namespace Avalonia.Build.Tasks
                                 MethodAttributes.Static | MethodAttributes.Private, asm.MainModule.TypeSystem.Void);
                             trampoline.Parameters.Add(new ParameterDefinition(classTypeDefinition));
                             classTypeDefinition.Methods.Add(trampoline);
-                            trampoline.Body.Instructions.Add(Instruction.Create(OpCodes.Ldnull));
+                            trampoline.Body.Instructions.Add(Instruction.Create(OpCodes.Call, getRootServiceProvider));
                             trampoline.Body.Instructions.Add(Instruction.Create(OpCodes.Ldarg_0));
                             trampoline.Body.Instructions.Add(Instruction.Create(OpCodes.Call, compiledPopulateMethod));
                             trampoline.Body.Instructions.Add(Instruction.Create(OpCodes.Ret));
@@ -243,7 +247,7 @@ namespace Avalonia.Build.Tasks
                                     i.Add(Instruction.Create(OpCodes.Newobj, parameterlessConstructor));
                                 else
                                 {
-                                    i.Add(Instruction.Create(OpCodes.Ldnull));
+                                    i.Add(Instruction.Create(OpCodes.Call, getRootServiceProvider));
                                     i.Add(Instruction.Create(OpCodes.Call, compiledBuildMethod));
                                 }
 

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs

@@ -37,7 +37,8 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
                 // We override XamlType.CanAssignTo in BindingXamlType so the results we get back
                 // from GetAllAmbientValues aren't necessarily of the correct type.
 
-                if (resourceProvider is IControl control && control.StylingParent != null)
+                if (AvaloniaXamlLoader.UseLegacyXamlLoader 
+                    && resourceProvider is IControl control && control.StylingParent != null)
                 {
                     // If we've got to a control that has a StylingParent then it's probably
                     // a top level control and its StylingParent is pointing to the global

src/Markup/Avalonia.Markup.Xaml/XamlIl/AvaloniaXamlIlRuntimeCompiler.cs

@@ -8,6 +8,7 @@ using System.Reflection;
 using System.Reflection.Emit;
 using System.Runtime.InteropServices;
 using Avalonia.Markup.Xaml.XamlIl.CompilerExtensions;
+using Avalonia.Markup.Xaml.XamlIl.Runtime;
 using Avalonia.Platform;
 using XamlIl.Transform;
 using XamlIl.TypeSystem;
@@ -54,8 +55,7 @@ namespace Avalonia.Markup.Xaml.XamlIl
                 _sreTypeSystem = new SreTypeSystem();
             if (_sreBuilder == null)
             {
-                _sreCanSave = AvaloniaLocator.Current.GetService<IRuntimePlatform>()?.GetRuntimeInfo().IsCoreClr ==
-                              false;
+                _sreCanSave = !(RuntimeInformation.FrameworkDescription.StartsWith(".NET Core"));
                 var name = new AssemblyName(Guid.NewGuid().ToString("N"));
                 if (_sreCanSave)
                 {
@@ -142,7 +142,7 @@ namespace Avalonia.Markup.Xaml.XamlIl
                 var createCb = Expression.Lambda<Func<IServiceProvider, object>>(
                     Expression.Convert(Expression.Call(
                         created.GetMethod(AvaloniaXamlIlCompiler.BuildName), isp), typeof(object)), isp).Compile();
-                return createCb(null);
+                return createCb(XamlIlRuntimeHelpers.GetRootServiceProviderV1());
             }
             else
             {
@@ -152,7 +152,7 @@ namespace Avalonia.Markup.Xaml.XamlIl
                 var populateCb = Expression.Lambda<Action<IServiceProvider, object>>(
                     Expression.Call(populate, isp, Expression.Convert(epar, populate.GetParameters()[1].ParameterType)),
                     isp, epar).Compile();
-                populateCb(null, rootInstance);
+                populateCb(XamlIlRuntimeHelpers.GetRootServiceProviderV1(), rootInstance);
                 return rootInstance;
             }
         }

src/Markup/Avalonia.Markup.Xaml/XamlIl/Runtime/XamlIlRuntimeHelpers.cs

@@ -124,5 +124,29 @@ namespace Avalonia.Markup.Xaml.XamlIl.Runtime
                     string.Join(",", lst.Select(e => $"`{e.ClrAssemblyName}:{e.ClrNamespace}.{name}`")));
             }
         }
+        
+        public static IServiceProvider GetRootServiceProviderV1()
+        {
+            return new RootServiceProvider();
+        }
+
+        class RootServiceProvider : IServiceProvider, IAvaloniaXamlIlParentStackProvider
+        {
+            public object GetService(Type serviceType)
+            {
+                if (serviceType == typeof(IAvaloniaXamlIlParentStackProvider))
+                    return this;
+                return null;
+            }
+
+            public IEnumerable<object> Parents
+            {
+                get
+                {
+                    if (Application.Current != null)
+                        yield return Application.Current;
+                }
+            }
+        }
     }
 }