Delay load static resources if necessary.

src/Markup/Avalonia.Markup.Xaml/Data/DelayedBinding.cs

@@ -3,9 +3,11 @@
 
 using System;
 using System.Collections.Generic;
+using System.Reflection;
 using System.Runtime.CompilerServices;
 using Avalonia.Controls;
 using Avalonia.Data;
+using Avalonia.Logging;
 
 namespace Avalonia.Markup.Xaml.Data
 {
@@ -50,7 +52,36 @@ namespace Avalonia.Markup.Xaml.Data
                     target.Initialized += ApplyBindings;
                 }
 
-                bindings.Add(new Entry(binding, property));
+                bindings.Add(new BindingEntry(property, binding));
+            }
+        }
+
+        /// <summary>
+        /// Adds a delayed binding to a control.
+        /// </summary>
+        /// <param name="target">The control.</param>
+        /// <param name="property">The property on the control to bind to.</param>
+        /// <param name="binding">The binding.</param>
+        public static void Add(IControl target, PropertyInfo property, Func<IControl, object> value)
+        {
+            if (target.IsInitialized)
+            {
+                property.SetValue(target, value(target));
+            }
+            else
+            {
+                List<Entry> bindings;
+
+                if (!_entries.TryGetValue(target, out bindings))
+                {
+                    bindings = new List<Entry>();
+                    _entries.Add(target, bindings);
+
+                    // TODO: Make this a weak event listener.
+                    target.Initialized += ApplyBindings;
+                }
+
+                bindings.Add(new ClrPropertyValueEntry(property, value));
             }
         }
 
@@ -60,13 +91,13 @@ namespace Avalonia.Markup.Xaml.Data
         /// <param name="control">The control.</param>
         public static void ApplyBindings(IControl control)
         {
-            List<Entry> bindings;
+            List<Entry> entries;
 
-            if (_entries.TryGetValue(control, out bindings))
+            if (_entries.TryGetValue(control, out entries))
             {
-                foreach (var binding in bindings)
+                foreach (var entry in entries)
                 {
-                    control.Bind(binding.Property, binding.Binding);
+                    entry.Apply(control);
                 }
 
                 _entries.Remove(control);
@@ -80,9 +111,14 @@ namespace Avalonia.Markup.Xaml.Data
             target.Initialized -= ApplyBindings;
         }
 
-        private class Entry
+        private abstract class Entry
+        {
+            public abstract void Apply(IControl control);
+        }
+
+        private class BindingEntry : Entry
         {
-            public Entry(IBinding binding, AvaloniaProperty property)
+            public BindingEntry(AvaloniaProperty property, IBinding binding)
             {
                 Binding = binding;
                 Property = property;
@@ -90,6 +126,41 @@ namespace Avalonia.Markup.Xaml.Data
 
             public IBinding Binding { get; }
             public AvaloniaProperty Property { get; }
+
+            public override void Apply(IControl control)
+            {
+                control.Bind(Property, Binding);
+            }
+        }
+
+        private class ClrPropertyValueEntry : Entry
+        {
+            public ClrPropertyValueEntry(PropertyInfo property, Func<IControl, object> value)
+            {
+                Property = property;
+                Value = value;
+            }
+
+            public PropertyInfo Property { get; }
+            public Func<IControl, object> Value { get; }
+
+            public override void Apply(IControl control)
+            {
+                try
+                {
+                    Property.SetValue(control, Value(control));
+                }
+                catch (Exception e)
+                {
+                    Logger.Error(
+                        LogArea.Property,
+                        control,
+                        "Error setting {Property} on {Target}: {Exception}",
+                        Property.Name,
+                        control,
+                        e);
+                }
+            }
         }
     }
 }

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

@@ -3,7 +3,9 @@
 
 using System;
 using System.ComponentModel;
+using System.Reflection;
 using Avalonia.Controls;
+using Avalonia.Markup.Xaml.Data;
 using Avalonia.Styling;
 using Portable.Xaml;
 using Portable.Xaml.ComponentModel;
@@ -32,6 +34,8 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             var resourceProviderType = schemaContext.GetXamlType(typeof(IResourceProvider));
             var resourceProviders = ambientProvider.GetAllAmbientValues(resourceProviderType);
 
+            // Look up the ambient context for IResourceProviders which might be able to give us
+            // the resource.
             foreach (IResourceProvider resourceProvider in resourceProviders)
             {
                 if (resourceProvider is IControl control && control.StylingParent != null)
@@ -47,7 +51,21 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
                 }
             }
 
+            // The resource still hasn't been found, so add a delayed one-time binding.
+            var provideTarget = context.GetService<IProvideValueTarget>();
+
+            if (provideTarget.TargetObject is IControl target &&
+                provideTarget.TargetProperty is PropertyInfo property)
+            {
+                DelayedBinding.Add(target, property, GetValue);
+            }
+
             return AvaloniaProperty.UnsetValue;
         }
+
+        private object GetValue(IControl control)
+        {
+            return control.FindResource(ResourceKey);
+        }
     }
 }

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

@@ -81,6 +81,33 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
+        [Fact]
+        public void StaticResource_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='{StaticResource 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 StaticResource_Can_Be_Assigned_To_Setter()
         {