Make TreeDataTemplate work.

samples/XamlTestApplication/Views/MainWindow.paml

@@ -70,14 +70,14 @@
                       </StackPanel>
                   </DropDown>
                   <TreeView Items="{Binding Nodes}">
-                    <!--<TreeView.DataTemplates>
+                    <TreeView.DataTemplates>
                       <TreeDataTemplate DataType="vm:TestNode" ItemsSource="{Binding Children}">
                         <StackPanel>
                           <TextBlock Text="{Binding Header}" FontSize="24"/>
                           <TextBlock Text="{Binding SubHeader}"/>
                         </StackPanel>
                       </TreeDataTemplate>
-                    </TreeView.DataTemplates>-->  
+                    </TreeView.DataTemplates>  
                   </TreeView>
                 </StackPanel>
             </TabItem>

src/Markup/Perspex.Markup.Xaml/Context/PerspexObjectAssembler.cs

@@ -16,6 +16,7 @@ namespace Perspex.Markup.Xaml.Context
         {
             var mapping = new DeferredLoaderMapping();
             mapping.Map<DataTemplate>(template => template.Content, new TemplateLoader());
+            mapping.Map<TreeDataTemplate>(template => template.Content, new TemplateLoader());
 
             var assembler = new ObjectAssembler(wiringContext, new TopDownValueContext(), objectAssemblerSettings);
             _objectAssembler = new TemplateHostingObjectAssembler(assembler, mapping);

src/Markup/Perspex.Markup.Xaml/Context/PerspexXamlMemberValuePlugin.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Linq;
 using System.Reactive.Linq;
+using System.Reflection;
 using Glass;
 using OmniXaml.ObjectAssembler;
 using OmniXaml.Typing;
@@ -57,39 +58,46 @@ namespace Perspex.Markup.Xaml.Context
 
         private void HandleXamlBindingDefinition(object instance, XamlBindingDefinition def)
         {
-            var perspexObject = instance as PerspexObject;
-
-            if (perspexObject == null)
+            if (_xamlMember.XamlType.UnderlyingType == typeof(XamlBindingDefinition))
             {
-                throw new InvalidOperationException(
-                    $"Cannot bind to an object of type '{instance.GetType()}");
-            }
+                // TODO: This should search base classes.
+                var property = instance.GetType().GetTypeInfo().GetDeclaredProperty(_xamlMember.Name);
 
-            var property = perspexObject.GetRegisteredProperties()
-                .FirstOrDefault(x => x.Name == _xamlMember.Name);
+                if (property == null || !property.CanWrite)
+                {
+                    throw new InvalidOperationException(
+                        $"Cannot assign to '{_xamlMember.Name}' on '{instance.GetType()}");
+                }
 
-            if (property == null)
-            {
-                throw new InvalidOperationException(
-                    $"Cannot find '{_xamlMember.Name}' on '{instance.GetType()}");
+                property.SetValue(instance, def);
             }
-
-            var binding = new XamlBinding(_propertyBinder.TypeConverterProvider)
+            else
             {
-                BindingMode = def.BindingMode,
-                SourcePropertyPath = def.SourcePropertyPath,
-            };
-
-            binding.Bind(perspexObject, property);
-        }
-
-        private void BindToDataContextWhenItsSet(XamlBindingDefinition definition)
-        {
-        //    var target = definition.Target;
-        //    var dataContext = target.DataContext;
-
-        //    var binding = _propertyBinder.GetBinding(target, definition.TargetProperty);
-        //    binding.BindToDataContext(dataContext);
+                var perspexObject = instance as PerspexObject;
+
+                if (perspexObject == null)
+                {
+                    throw new InvalidOperationException(
+                        $"Cannot bind to an object of type '{instance.GetType()}");
+                }
+
+                var property = perspexObject.GetRegisteredProperties()
+                    .FirstOrDefault(x => x.Name == _xamlMember.Name);
+
+                if (property == null)
+                {
+                    throw new InvalidOperationException(
+                        $"Cannot find '{_xamlMember.Name}' on '{instance.GetType()}");
+                }
+
+                var binding = new XamlBinding(_propertyBinder.TypeConverterProvider)
+                {
+                    BindingMode = def.BindingMode,
+                    SourcePropertyPath = def.SourcePropertyPath,
+                };
+
+                binding.Bind(perspexObject, property);
+            }
         }
 
         // ReSharper disable once MemberCanBePrivate.Global

src/Markup/Perspex.Markup.Xaml/Templates/TreeDataTemplate.cs

@@ -3,9 +3,10 @@
 
 using System;
 using System.Collections;
-using OmniXaml.Attributes;
+using System.Reactive.Linq;
 using Perspex.Controls;
 using Perspex.Controls.Templates;
+using Perspex.Markup.Binding;
 using Perspex.Markup.Xaml.Binding;
 
 namespace Perspex.Markup.Xaml.Templates
@@ -14,7 +15,7 @@ namespace Perspex.Markup.Xaml.Templates
     {
         public Type DataType { get; set; }
         public TemplateContent Content { get; set; }
-        public XamlBinding ItemsSource { get; set; }
+        public XamlBindingDefinition ItemsSource { get; set; }
 
         public bool Match(object data)
         {
@@ -30,7 +31,8 @@ namespace Perspex.Markup.Xaml.Templates
         {
             if (ItemsSource != null)
             {
-                // TODO: Get value of ItemsSource here.
+                var obs = new ExpressionObserver(item, ItemsSource.SourcePropertyPath);
+                return obs.Take(1).Wait().Value as IEnumerable;
             }
 
             return null;