Added DynamicResourceExtension.

src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj

@@ -34,6 +34,7 @@
         <Compile Include="Converters\MatrixTypeConverter.cs" />
         <Compile Include="Converters\RectTypeConverter.cs" />
         <Compile Include="Converters\SetterValueTypeConverter.cs" />
+        <Compile Include="MarkupExtensions\DynamicResourceExtension.cs" />
         <Compile Include="MarkupExtensions\StaticResourceExtension.cs" />
         <Compile Include="MarkupExtensions\StyleIncludeExtension.cs" />
         <Compile Include="PortableXaml\AvaloniaXamlContext.cs" />

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

@@ -0,0 +1,41 @@
+// 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;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Portable.Xaml.Markup;
+
+namespace Avalonia.Markup.Xaml.MarkupExtensions
+{
+    public class DynamicResourceExtension : MarkupExtension, IBinding
+    {
+        public DynamicResourceExtension()
+        {
+        }
+
+        public DynamicResourceExtension(string resourceKey)
+        {
+            ResourceKey = resourceKey;
+        }
+
+        public string ResourceKey { get; set; }
+
+        public override object ProvideValue(IServiceProvider serviceProvider) => this;
+
+        InstancedBinding IBinding.Initiate(
+            IAvaloniaObject target,
+            AvaloniaProperty targetProperty,
+            object anchor,
+            bool enableDataValidation)
+        {
+            if (target is IControl control)
+            {
+                var resource = control.FindResource(ResourceKey);
+                return new InstancedBinding(resource);
+            }
+
+            return null;
+        }
+    }
+}

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceTests.cs

@@ -0,0 +1,285 @@
+// 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;
+using System.Linq;
+using Avalonia.Controls;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Markup.Xaml.Data;
+using Avalonia.Media;
+using Avalonia.Styling;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
+{
+    public class DynamicResourceTests
+    {
+        [Fact]
+        public void DynamicResource_Can_Be_Assigned_To_Property()
+        {
+            var xaml = @"
+<UserControl xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <UserControl.Resources>
+        <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+    </UserControl.Resources>
+
+    <Border Name='border' Background='{DynamicResource brush}'/>
+</UserControl>";
+
+            var loader = new AvaloniaXamlLoader();
+            var userControl = (UserControl)loader.Load(xaml);
+            var border = userControl.FindControl<Border>("border");
+
+            DelayedBinding.ApplyBindings(border);
+
+            var brush = (SolidColorBrush)border.Background;
+            Assert.Equal(0xff506070, brush.Color.ToUint32());
+        }
+
+        [Fact]
+        public void DynamicResource_From_Style_Can_Be_Assigned_To_Property()
+        {
+            var xaml = @"
+<UserControl xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <UserControl.Styles>
+        <Style>
+            <Style.Resources>
+                <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+            </Style.Resources>
+        </Style>
+    </UserControl.Styles>
+
+    <Border Name='border' Background='{DynamicResource brush}'/>
+</UserControl>";
+
+            var loader = new AvaloniaXamlLoader();
+            var userControl = (UserControl)loader.Load(xaml);
+            var border = userControl.FindControl<Border>("border");
+
+            DelayedBinding.ApplyBindings(border);
+
+            var brush = (SolidColorBrush)border.Background;
+            Assert.Equal(0xff506070, brush.Color.ToUint32());
+        }
+
+        [Fact]
+        public void DynamicResource_From_Application_Can_Be_Assigned_To_Property_In_Window()
+        {
+            using (StyledWindow())
+            {
+                Application.Current.Resources.Add("brush", new SolidColorBrush(0xff506070));
+
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Border Name='border' Background='{DynamicResource brush}'/>
+</Window>";
+
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var border = window.FindControl<Border>("border");
+
+                var brush = (SolidColorBrush)border.Background;
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        [Fact]
+        public void DynamicResource_From_Application_Can_Be_Assigned_To_Property_In_UserControl()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                Application.Current.Resources.Add("brush", new SolidColorBrush(0xff506070));
+
+                var xaml = @"
+<UserControl xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Border Name='border' Background='{DynamicResource brush}'/>
+</UserControl>";
+
+                var loader = new AvaloniaXamlLoader();
+                var userControl = (UserControl)loader.Load(xaml);
+                var border = userControl.FindControl<Border>("border");
+
+                // We don't actually know where the global styles are until we attach the control
+                // to a window, as Window has StylingParent set to Application.
+                var window = new Window { Content = userControl };
+                window.Show();
+
+                var brush = (SolidColorBrush)border.Background;
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        [Fact]
+        public void DynamicResource_Can_Be_Assigned_To_Setter()
+        {
+            using (StyledWindow())
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Resources>
+        <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+    </Window.Resources>
+    <Window.Styles>
+        <Style Selector='Button'>
+            <Setter Property='Background' Value='{DynamicResource brush}'/>
+        </Style>
+    </Window.Styles>
+    <Button Name='button'/>
+</Window>";
+
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+                var brush = (SolidColorBrush)button.Background;
+
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        [Fact]
+        public void DynamicResource_From_Style_Can_Be_Assigned_To_Setter()
+        {
+            using (StyledWindow())
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <Style>
+            <Style.Resources>
+                <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+            </Style.Resources>
+        </Style>
+        <Style Selector='Button'>
+            <Setter Property='Background' Value='{DynamicResource brush}'/>
+        </Style>
+    </Window.Styles>
+    <Button Name='button'/>
+</Window>";
+
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+                var brush = (SolidColorBrush)button.Background;
+
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        [Fact]
+        public void DynamicResource_Can_Be_Assigned_To_Setter_In_Styles_File()
+        {
+            var styleXaml = @"
+<Styles xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Styles.Resources>
+        <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+    </Styles.Resources>
+
+    <Style Selector='Border'>
+        <Setter Property='Background' Value='{DynamicResource brush}'/>
+    </Style>
+</Styles>";
+
+            using (StyledWindow(assets: ("test:style.xaml", styleXaml)))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <StyleInclude Source='test:style.xaml'/>
+    </Window.Styles>
+    <Border Name='border'/>
+</Window>";
+
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var border = window.FindControl<Border>("border");
+                var brush = (SolidColorBrush)border.Background;
+
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        [Fact]
+        public void DynamicResource_Can_Be_Assigned_To_Property_In_ControlTemplate_In_Styles_File()
+        {
+            var styleXaml = @"
+<Styles xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Styles.Resources>
+        <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+    </Styles.Resources>
+
+    <Style Selector='Button'>
+        <Setter Property='Template'>
+            <ControlTemplate>
+                <Border Name='border' Background='{DynamicResource brush}'/>
+            </ControlTemplate>
+        </Setter>
+    </Style>
+</Styles>";
+
+            using (StyledWindow(assets: ("test:style.xaml", styleXaml)))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <StyleInclude Source='test:style.xaml'/>
+    </Window.Styles>
+    <Button Name='button'/>
+</Window>";
+
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.Show();
+
+                var border = (Border)button.GetVisualChildren().Single();
+                var brush = (SolidColorBrush)border.Background;
+
+                Assert.Equal(0xff506070, brush.Color.ToUint32());
+            }
+        }
+
+        private IDisposable StyledWindow(params (string, string)[] assets)
+        {
+            var services = TestServices.StyledWindow.With(
+                assetLoader: new MockAssetLoader(assets),
+                theme: () => new Styles
+                {
+                    WindowStyle(),
+                });
+
+            return UnitTestApplication.Start(services);
+        }
+
+        private Style WindowStyle()
+        {
+            return new Style(x => x.OfType<Window>())
+            {
+                Setters =
+                {
+                    new Setter(
+                        Window.TemplateProperty,
+                        new FuncControlTemplate<Window>(x =>
+                            new ContentPresenter
+                            {
+                                Name = "PART_ContentPresenter",
+                                [!ContentPresenter.ContentProperty] = x[!Window.ContentProperty],
+                            }))
+                }
+            };
+        }
+    }
+}

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/StaticResourceTests.cs

@@ -17,7 +17,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
     public class StaticResourceTests
     {
         [Fact]
-        public void StaticResource_Style_Can_Be_Assigned_To_Property()
+        public void StaticResource_Can_Be_Assigned_To_Property()
         {
             var xaml = @"
 <UserControl xmlns='https://github.com/avaloniaui'