Started implementing TreeDataTemplate.

Binding system needs to be updated first.

samples/XamlTestApplication/ViewModels/MainWindowViewModel.cs

@@ -15,8 +15,44 @@ namespace XamlTestApplication.ViewModels
             {
                 Items.Add(new TestItem($"Item {i}", $"Item {i} Value"));
             }
+
+            Nodes = new List<TestNode>
+            {
+                new TestNode
+                {
+                    Header = "Root",
+                    SubHeader = "Root Item",
+                    Children = new[]
+                    {
+                        new TestNode
+                        {
+                            Header = "Child 1",
+                            SubHeader = "Child 1 Value",
+                        },
+                        new TestNode
+                        {
+                            Header = "Child 2",
+                            SubHeader = "Child 2 Value",
+                            Children = new[]
+                            {
+                                new TestNode
+                                {
+                                    Header = "Grandchild",
+                                    SubHeader = "Grandchild Value",
+                                },
+                                new TestNode
+                                {
+                                    Header = "Grandmaster Flash",
+                                    SubHeader = "White Lines",
+                                },
+                            }
+                        },
+                    }
+                }
+            };
         }
 
         public List<TestItem> Items { get; }
+        public List<TestNode> Nodes { get; }
     }
 }

samples/XamlTestApplication/Views/MainWindow.paml

@@ -60,16 +60,26 @@
                       </DataTemplate>
                     </ListBox.DataTemplates>
                   </ListBox>
-                    <DropDown VerticalAlignment="Center">
+                  <DropDown VerticalAlignment="Center">
+                      <StackPanel>
+                          <TextBlock Text="Item 1" FontSize="24" />
+                          <TextBlock Text="Item 1 Value" />
+                      </StackPanel>
+                      <StackPanel>
+                          <TextBlock Text="Item 2" FontSize="24" />
+                          <TextBlock Text="Item 2 Value" />
+                      </StackPanel>
+                  </DropDown>
+                  <TreeView Items="{Binding Nodes}">
+                    <TreeView.DataTemplates>
+                      <TreeDataTemplate DataType="vm:TestNode" ItemsSource="{Binding Children}">
                         <StackPanel>
-                            <TextBlock Text="Item 1" FontSize="24" />
-                            <TextBlock Text="Item 1 Value" />
-                        </StackPanel>
-                        <StackPanel>
-                            <TextBlock Text="Item 2" FontSize="24" />
-                            <TextBlock Text="Item 2 Value" />
+                          <TextBlock Text="{Binding Header}" FontSize="24"/>
+                          <TextBlock Text="{Binding SubHeader}"/>
                         </StackPanel>
-                    </DropDown>
+                      </TreeDataTemplate>
+                    </TreeView.DataTemplates>  
+                  </TreeView>
                 </StackPanel>
             </TabItem>
             <TabItem Header="Layout">

samples/XamlTestApplication/Views/TestNode.cs

@@ -0,0 +1,14 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System.Collections.Generic;
+
+namespace XamlTestApplication.ViewModels
+{
+    public class TestNode
+    {
+        public string Header { get; set; }
+        public string SubHeader { get; set; }
+        public IEnumerable<TestNode> Children { get; set; }
+    }
+}

samples/XamlTestApplication/XamlTestApplication.csproj

@@ -80,6 +80,7 @@
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="ViewModels\MainWindowViewModel.cs" />
+    <Compile Include="Views\TestNode.cs" />
     <Compile Include="ViewModels\TestItem.cs" />
     <Compile Include="Views\MainWindow.cs" />
   </ItemGroup>

src/Markup/Perspex.Markup.Xaml/Perspex.Markup.Xaml.csproj

@@ -245,6 +245,7 @@
     <Compile Include="Context\PerspexXamlType.cs" />
     <Compile Include="Templates\DataTemplate.cs" />
     <Compile Include="PerspexXamlLoader.cs" />
+    <Compile Include="Templates\TreeDataTemplate.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="app.config" />

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

@@ -12,7 +12,6 @@ namespace Perspex.Markup.Xaml.Templates
     public class DataTemplate : IDataTemplate
     {
         public Type DataType { get; set; }
-
         public TemplateContent Content { get; set; }
 
         public bool Match(object data)
@@ -25,12 +24,7 @@ namespace Perspex.Markup.Xaml.Templates
             return DataType == data.GetType();
         }
 
-        public IControl Build(object param)
-        {
-            return CreateVisualTreeForItem(param);
-        }
-
-        private Control CreateVisualTreeForItem(object data)
+        public IControl Build(object data)
         {
             var visualTreeForItem = Content.Load();
             visualTreeForItem.DataContext = data;

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

@@ -0,0 +1,52 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using System.Collections;
+using OmniXaml.Attributes;
+using Perspex.Controls;
+using Perspex.Controls.Templates;
+using Perspex.Markup.Xaml.DataBinding;
+
+namespace Perspex.Markup.Xaml.Templates
+{
+    [ContentProperty("Content")]
+    public class TreeDataTemplate : ITreeDataTemplate
+    {
+        public Type DataType { get; set; }
+        public TemplateContent Content { get; set; }
+        public XamlBinding ItemsSource { get; set; }
+
+        public bool Match(object data)
+        {
+            if (DataType == null)
+            {
+                throw new InvalidOperationException("DataTemplate must have a DataType.");
+            }
+
+            return DataType == data.GetType();
+        }
+
+        public IEnumerable ItemsSelector(object item)
+        {
+            if (ItemsSource != null)
+            {
+                // TODO: Get value of ItemsSource here.
+            }
+
+            return null;
+        }
+
+        public bool IsExpanded(object item)
+        {
+            return true;
+        }
+
+        public IControl Build(object data)
+        {
+            var visualTreeForItem = Content.Load();
+            visualTreeForItem.DataContext = data;
+            return visualTreeForItem;
+        }
+    }
+}