Move path parsing into the binding extension. Our path shorthands will only work from XAML now. Now we can look up types.

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

@@ -91,55 +91,50 @@ namespace Avalonia.Markup.Xaml.Data
             bool enableDataValidation = false)
         {
             Contract.Requires<ArgumentNullException>(target != null);
-
+            
-            var pathInfo = ParsePath(Path);
-            ValidateState(pathInfo);
             enableDataValidation = enableDataValidation && Priority == BindingPriority.LocalValue;
-
+            
-            var elementName = ElementName ?? pathInfo.ElementName;
-            var relativeSource = RelativeSource ?? pathInfo.RelativeSource;
-
             ExpressionObserver observer;
 
-            if (elementName != null)
+            if (ElementName != null)
             {
                 observer = CreateElementObserver(
                     (target as IControl) ?? (anchor as IControl),
-                    elementName,
+                    ElementName,
-                    pathInfo.Path);
+                    Path);
             }
             else if (Source != null)
             {
-                observer = CreateSourceObserver(Source, pathInfo.Path, enableDataValidation);
+                observer = CreateSourceObserver(Source, Path, enableDataValidation);
             }
-            else if (relativeSource == null || relativeSource.Mode == RelativeSourceMode.DataContext)
+            else if (RelativeSource == null || RelativeSource.Mode == RelativeSourceMode.DataContext)
             {
                 observer = CreateDataContexObserver(
                     target,
-                    pathInfo.Path,
+                    Path,
                     targetProperty == Control.DataContextProperty,
                     anchor,
                     enableDataValidation);
             }
-            else if (relativeSource.Mode == RelativeSourceMode.Self)
+            else if (RelativeSource.Mode == RelativeSourceMode.Self)
             {
-                observer = CreateSourceObserver(target, pathInfo.Path, enableDataValidation);
+                observer = CreateSourceObserver(target, Path, enableDataValidation);
             }
-            else if (relativeSource.Mode == RelativeSourceMode.TemplatedParent)
+            else if (RelativeSource.Mode == RelativeSourceMode.TemplatedParent)
             {
-                observer = CreateTemplatedParentObserver(target, pathInfo.Path);
+                observer = CreateTemplatedParentObserver(target, Path);
             }
-            else if (relativeSource.Mode == RelativeSourceMode.FindAncestor)
+            else if (RelativeSource.Mode == RelativeSourceMode.FindAncestor)
             {
-                if (relativeSource.AncestorType == null)
+                if (RelativeSource.AncestorType == null)
                 {
                     throw new InvalidOperationException("AncestorType must be set for RelativeSourceModel.FindAncestor.");
                 }
 
                 observer = CreateFindAncestorObserver(
                     (target as IControl) ?? (anchor as IControl),
-                    relativeSource,
+                    RelativeSource,
-                    pathInfo.Path);
+                    Path);
             }
             else
             {
@@ -168,128 +163,6 @@ namespace Avalonia.Markup.Xaml.Data
             return new InstancedBinding(subject, Mode, Priority);
         }
 
-        private static PathInfo ParsePath(string path)
-        {
-            var result = new PathInfo();
-
-            if (string.IsNullOrWhiteSpace(path) || path == ".")
-            {
-                result.Path = string.Empty;
-            }
-            else if (path.StartsWith("#"))
-            {
-                var dot = path.IndexOf('.');
-
-                if (dot != -1)
-                {
-                    result.Path = path.Substring(dot + 1);
-                    result.ElementName = path.Substring(1, dot - 1);
-                }
-                else
-                {
-                    result.Path = string.Empty;
-                    result.ElementName = path.Substring(1);
-                }
-            }
-            else if (path.StartsWith("$"))
-            {
-                var relativeSource = new RelativeSource();
-                result.RelativeSource = relativeSource;
-                var dot = path.IndexOf('.');
-                string relativeSourceMode;
-                if (dot != -1)
-                {
-                    result.Path = path.Substring(dot + 1);
-                    relativeSourceMode = path.Substring(1, dot - 1);
-                }
-                else
-                {
-                    result.Path = string.Empty;
-                    relativeSourceMode = path.Substring(1);
-                }
-
-                if (relativeSourceMode == "self")
-                {
-                    relativeSource.Mode = RelativeSourceMode.Self;
-                }
-                else if(relativeSourceMode == "parent")
-                {
-                    relativeSource.Mode = RelativeSourceMode.FindAncestor;
-                    relativeSource.AncestorType = typeof(IControl);
-                    relativeSource.AncestorLevel = 1;
-                }
-                else if(relativeSourceMode.StartsWith("parent["))
-                {
-                    relativeSource.Mode = RelativeSourceMode.FindAncestor;
-                    var parentConfigStart = relativeSourceMode.IndexOf('[');
-                    if (!relativeSourceMode.EndsWith("]"))
-                    {
-                        throw new InvalidOperationException("Invalid RelativeSource binding syntax. Expected matching ']' for '['.");
-                    }
-                    var parentConfigParams = relativeSourceMode.Substring(parentConfigStart + 1).TrimEnd(']').Split(',');
-                    if (parentConfigParams.Length > 2 || parentConfigParams.Length == 0)
-                    {
-                        throw new InvalidOperationException("Expected either 1 or 2 parameters for RelativeSource binding syntax");
-                    }
-                    else if (parentConfigParams.Length == 1)
-                    {
-                        if (int.TryParse(parentConfigParams[0], out int level))
-                        {
-                            relativeSource.AncestorType = typeof(IControl);
-                            relativeSource.AncestorLevel = level + 1;
-                        }
-                        else
-                        {
-                            relativeSource.AncestorType = LookupAncestorType(parentConfigParams[0]);
-                        }
-                    }
-                    else
-                    {
-                        relativeSource.AncestorType = LookupAncestorType(parentConfigParams[0]);
-                        relativeSource.AncestorLevel = int.Parse(parentConfigParams[1]) + 1;
-                    }
-                }
-                else
-                {
-                    throw new InvalidOperationException($"Invalid RelativeSource binding syntax: {relativeSourceMode}");
-                }
-            }
-            else
-            {
-                result.Path = path;
-            }
-
-            return result;
-        }
-
-        private static Type LookupAncestorType(string ancestorTypeName)
-        {
-            //TODO: What is our syntax for type lookup here?
-            throw new NotImplementedException();
-        }
-
-        private void ValidateState(PathInfo pathInfo)
-        {
-            if (pathInfo.ElementName != null && ElementName != null)
-            {
-                throw new InvalidOperationException(
-                    "ElementName property cannot be set when an #elementName path is provided.");
-            }
-
-            if (pathInfo.RelativeSource != null && RelativeSource != null)
-            {
-                throw new InvalidOperationException(
-                    "ElementName property cannot be set when a $self or $parent path is provided.");
-            }
-
-            if ((pathInfo.ElementName != null || ElementName != null) &&
-                (pathInfo.RelativeSource != null || RelativeSource != null))
-            {
-                throw new InvalidOperationException(
-                    "ElementName property cannot be set with a RelativeSource.");
-            }
-        }
-
         private ExpressionObserver CreateDataContexObserver(
             IAvaloniaObject target,
             string path,

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

@@ -7,8 +7,13 @@ using System;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions
 {
+    using Avalonia.Controls;
+    using Avalonia.Styling;
+    using Portable.Xaml;
+    using Portable.Xaml.ComponentModel;
     using Portable.Xaml.Markup;
     using PortableXaml;
+    using System.ComponentModel;
 
     [MarkupExtensionReturnType(typeof(IBinding))]
     public class BindingExtension : MarkupExtension
@@ -24,19 +29,181 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
 
         public override object ProvideValue(IServiceProvider serviceProvider)
         {
-            var b = new Binding
+            var descriptorContext = (ITypeDescriptorContext)serviceProvider;
+
+            var pathInfo = ParsePath(Path, descriptorContext);
+            ValidateState(pathInfo);
+
+            return XamlBinding.FromMarkupExtensionContext(
+                new Binding
+                {
+                    Converter = Converter,
+                    ConverterParameter = ConverterParameter,
+                    ElementName = pathInfo.ElementName ?? ElementName,
+                    FallbackValue = FallbackValue,
+                    Mode = Mode,
+                    Path = pathInfo.Path,
+                    Priority = Priority,
+                    RelativeSource = pathInfo.RelativeSource ?? RelativeSource,
+                },
+                serviceProvider);
+        }
+
+        private class PathInfo
+        {
+            public string Path { get; set; }
+            public string ElementName { get; set; }
+            public RelativeSource RelativeSource { get; set; }
+        }
+
+        private void ValidateState(PathInfo pathInfo)
+        {
+            if (pathInfo.ElementName != null && ElementName != null)
+            {
+                throw new InvalidOperationException(
+                    "ElementName property cannot be set when an #elementName path is provided.");
+            }
+
+            if (pathInfo.RelativeSource != null && RelativeSource != null)
+            {
+                throw new InvalidOperationException(
+                    "ElementName property cannot be set when a $self or $parent path is provided.");
+            }
+
+            if ((pathInfo.ElementName != null || ElementName != null) &&
+                (pathInfo.RelativeSource != null || RelativeSource != null))
+            {
+                throw new InvalidOperationException(
+                    "ElementName property cannot be set with a RelativeSource.");
+            }
+        }
+
+        private static PathInfo ParsePath(string path, ITypeDescriptorContext context)
+        {
+            var result = new PathInfo();
+
+            if (string.IsNullOrWhiteSpace(path) || path == ".")
             {
-                Converter = Converter,
+                result.Path = string.Empty;
-                ConverterParameter = ConverterParameter,
+            }
-                ElementName = ElementName,
+            else if (path.StartsWith("#"))
-                FallbackValue = FallbackValue,
+            {
-                Mode = Mode,
+                var dot = path.IndexOf('.');
-                Path = Path,
+
-                Priority = Priority,
+                if (dot != -1)
-                RelativeSource = RelativeSource
+                {
-            };
+                    result.Path = path.Substring(dot + 1);
+                    result.ElementName = path.Substring(1, dot - 1);
+                }
+                else
+                {
+                    result.Path = string.Empty;
+                    result.ElementName = path.Substring(1);
+                }
+            }
+            else if (path.StartsWith("$"))
+            {
+                var relativeSource = new RelativeSource();
+                result.RelativeSource = relativeSource;
+                var dot = path.IndexOf('.');
+                string relativeSourceMode;
+                if (dot != -1)
+                {
+                    result.Path = path.Substring(dot + 1);
+                    relativeSourceMode = path.Substring(1, dot - 1);
+                }
+                else
+                {
+                    result.Path = string.Empty;
+                    relativeSourceMode = path.Substring(1);
+                }
+
+                if (relativeSourceMode == "self")
+                {
+                    relativeSource.Mode = RelativeSourceMode.Self;
+                }
+                else if (relativeSourceMode == "parent")
+                {
+                    relativeSource.Mode = RelativeSourceMode.FindAncestor;
+                    relativeSource.AncestorType = typeof(IControl);
+                    relativeSource.AncestorLevel = 1;
+                }
+                else if (relativeSourceMode.StartsWith("parent["))
+                {
+                    relativeSource.Mode = RelativeSourceMode.FindAncestor;
+                    var parentConfigStart = relativeSourceMode.IndexOf('[');
+                    if (!relativeSourceMode.EndsWith("]"))
+                    {
+                        throw new InvalidOperationException("Invalid RelativeSource binding syntax. Expected matching ']' for '['.");
+                    }
+                    var parentConfigParams = relativeSourceMode.Substring(parentConfigStart + 1).TrimEnd(']').Split(';');
+                    if (parentConfigParams.Length > 2 || parentConfigParams.Length == 0)
+                    {
+                        throw new InvalidOperationException("Expected either 1 or 2 parameters for RelativeSource binding syntax");
+                    }
+                    else if (parentConfigParams.Length == 1)
+                    {
+                        if (int.TryParse(parentConfigParams[0], out int level))
+                        {
+                            relativeSource.AncestorType = typeof(IControl);
+                            relativeSource.AncestorLevel = level + 1;
+                        }
+                        else
+                        {
+                            relativeSource.AncestorType = LookupAncestorType(parentConfigParams[0], context);
+                        }
+                    }
+                    else
+                    {
+                        relativeSource.AncestorType = LookupAncestorType(parentConfigParams[0], context);
+                        relativeSource.AncestorLevel = int.Parse(parentConfigParams[1]) + 1;
+                    }
+                }
+                else
+                {
+                    throw new InvalidOperationException($"Invalid RelativeSource binding syntax: {relativeSourceMode}");
+                }
+            }
+            else
+            {
+                result.Path = path;
+            }
+
+            return result;
+        }
+
+        private static Type LookupAncestorType(string ancestorTypeName, ITypeDescriptorContext context)
+        {
+            var parts = ancestorTypeName.Split(':');
+            if (parts.Length == 0 || parts.Length > 2)
+            {
+                throw new InvalidOperationException("Invalid type name");
+            }
+
+            if (parts.Length == 1)
+            {
+                return context.ResolveType(string.Empty, parts[0]);
+            }
+            else
+            {
+                return context.ResolveType(parts[0], parts[1]);
+            }
+        }
+
+        private static object GetDefaultAnchor(ITypeDescriptorContext context)
+        {
+            object anchor = null;
+
+            // The target is not a control, so we need to find an anchor that will let us look
+            // up named controls and style resources. First look for the closest IControl in
+            // the context.
+            anchor = context.GetFirstAmbientValue<IControl>();
 
-            return XamlBinding.FromMarkupExtensionContext(b, serviceProvider);
+            // If a control was not found, then try to find the highest-level style as the XAML
+            // file could be a XAML file containing only styles.
+            return anchor ??
+                    context.GetService<IRootObjectProvider>()?.RootObject as IStyle ??
+                    context.GetLastOrDefaultAmbientValue<IStyle>();
         }
 
         public IValueConverter Converter { get; set; }

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

@@ -127,6 +127,56 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
+        [Fact]
+        public void Binding_To_Ancestor_Of_Type_With_Shorthand_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Border Name='border1'>
+      <Border Name='border2'>
+        <Button Name='button' Content='{Binding $parent[Border].Name}'/>
+      </Border>
+    </Border>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+
+                Assert.Equal("border2", button.Content);
+            }
+        }
+
+        [Fact]
+        public void Binding_To_Second_Ancestor_With_Shorthand_And_Type_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Border Name='border1'>
+      <Border Name='border2'>
+        <Button Name='button' Content='{Binding $parent[Border; 1].Name}'/>
+      </Border>
+    </Border>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+
+                Assert.Equal("border1", button.Content);
+            }
+        }
+
         [Fact]
         public void Binding_To_Second_Ancestor_With_Shorthand_Works()
         {