member selector support member path

src/Markup/Avalonia.Markup.Xaml/Templates/MemberSelector.cs

@@ -1,20 +1,47 @@
-// Copyright (c) The Avalonia Project. All rights reserved.
+// 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.Reflection;
 using Avalonia.Controls.Templates;
+using Avalonia.Markup.Data;
+using System;
 
 namespace Avalonia.Markup.Xaml.Templates
 {
     public class MemberSelector : IMemberSelector
     {
-        public string MemberName { get; set; }
+        public string MemberName
+        {
+            get { return _memberName; }
+            set
+            {
+                if (_memberName != value)
+                {
+                    _memberName = value;
+                    _expressionNode = null;
+                    _memberValueNode = null;
+                }
+            }
+        }
 
         public object Select(object o)
         {
-            // TODO: Handle nested property paths, changing values etc.
-            var property = o.GetType().GetRuntimeProperty(MemberName);
-            return property?.GetValue(o);
+            if (_expressionNode == null)
+            {
+                _expressionNode = ExpressionNodeBuilder.Build(MemberName);
+
+                _memberValueNode = _expressionNode;
+
+                while (_memberValueNode.Next != null)
+                    _memberValueNode = _memberValueNode.Next;
+            }
+
+            _expressionNode.Target = new WeakReference(o);
+
+            return _memberValueNode.CurrentValue.Target;
         }
+
+        private ExpressionNode _expressionNode;
+        private string _memberName;
+        private ExpressionNode _memberValueNode;
     }
-}
+}

src/Markup/Avalonia.Markup/Properties/AssemblyInfo.cs

@@ -7,4 +7,5 @@ using System.Runtime.CompilerServices;
 
 [assembly: AssemblyTitle("Avalonia.Markup")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Markup")]
-[assembly: InternalsVisibleTo("Avalonia.Markup.UnitTests")]
+[assembly: InternalsVisibleTo("Avalonia.Markup.UnitTests")]
+[assembly: InternalsVisibleTo("Avalonia.Markup.Xaml")]