Lookup property on correct object.

src/Markup/Perspex.Markup.Xaml/Binding/XamlTemplateBinding.cs

@@ -40,7 +40,9 @@ namespace Perspex.Markup.Xaml.Binding
             PerspexProperty targetProperty,
             PerspexObject templatedParent)
         {
-            var sourceProperty = PerspexPropertyRegistry.Instance.FindRegistered(instance.GetType(), SourcePropertyPath);
+            var sourceProperty = PerspexPropertyRegistry.Instance.FindRegistered(
+                templatedParent, 
+                SourcePropertyPath);
 
             if (sourceProperty == null)
             {

src/Perspex.Base/PerspexPropertyRegistry.cs

@@ -179,6 +179,28 @@ namespace Perspex
             return results.FirstOrDefault(x => x.Name == propertyName);
         }
 
+
+        /// <summary>
+        /// Finds a registered property on an object by name.
+        /// </summary>
+        /// <param name="o">The object.</param>
+        /// <param name="name">
+        /// The property name. If an attached property it should be in the form 
+        /// "OwnerType.PropertyName".
+        /// </param>
+        /// <returns>
+        /// The registered property or null if no matching property found.
+        /// </returns>
+        public PerspexProperty FindRegistered(PerspexObject o, string name)
+        {
+            return FindRegistered(o.GetType(), name);
+        }
+
+        /// <summary>
+        /// Returns a type and all its base types.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        /// <returns>The type and all its base types.</returns>
         private IEnumerable<string> GetImplementedTypes(Type type)
         {
             while (type != null)