Correctly set TreeView item DataContexts.

Also added a few tests for TreeView.

src/Perspex.Controls/Generators/TreeItemContainerGenerator.cs

@@ -165,22 +165,33 @@ namespace Perspex.Controls.Generators
         /// <returns>The created container control.</returns>
         protected virtual T CreateContainer(object item)
         {
-            T result = item as T;
+            var container = item as T;
 
-            if (result == null)
+            if (item == null)
+            {
+                return null;
+            }
+            else if (container != null)
+            {
+                return container;
+            }
+            else
             {
                 var template = GetTreeDataTemplate(item);
-
-                result = new T
+                var result = new T
                 {
                     Header = template.Build(item),
                     Items = template.ItemsSelector(item),
                     IsExpanded = template.IsExpanded(item),
-                    DataContext = item,
                 };
-            }
 
-            return result;
+                if (!(item is IControl))
+                {
+                    result.DataContext = item;
+                }
+
+                return result;
+            }
         }
 
         /// <summary>

tests/Perspex.Controls.UnitTests/TreeViewTests.cs

@@ -0,0 +1,101 @@
+// 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.Linq;
+using Perspex.Controls;
+using Perspex.Controls.Presenters;
+using Perspex.Controls.Templates;
+using Perspex.LogicalTree;
+using Perspex.Styling;
+using Xunit;
+
+namespace Perspex.Controls.UnitTests
+{
+    public class TreeViewTests
+    {
+        [Fact]
+        public void LogicalChildren_Should_Be_Set()
+        {
+            var target = new TreeView
+            {
+                Template = new ControlTemplate(CreateTreeViewTemplate),
+                Items = new[] { "Foo", "Bar", "Baz " },
+            };
+
+            target.ApplyTemplate();
+
+            Assert.Equal(3, target.GetLogicalChildren().Count());
+
+            foreach (var child in target.GetLogicalChildren())
+            {
+                Assert.IsType<TreeViewItem>(child);
+            }
+        }
+
+        [Fact]
+        public void DataContexts_Should_Be_Correctly_Set()
+        {
+            var items = new object[]
+            {
+                "Foo",
+                new Item("Bar"),
+                new TextBlock { Text = "Baz" },
+                new TreeViewItem { Header = "Qux" },
+            };
+
+            var target = new TreeView
+            {
+                Template = new ControlTemplate(CreateTreeViewTemplate),
+                DataContext = "Base",
+                DataTemplates = new DataTemplates
+                {
+                    new FuncDataTemplate<Item>(x => new Button { Content = x })
+                },
+                Items = items,
+            };
+
+            target.ApplyTemplate();
+
+            var dataContexts = target.Presenter.Panel.Children
+                .Cast<Control>()
+                .Select(x => x.DataContext)
+                .ToList();
+
+            Assert.Equal(
+                new object[] { items[0], items[1], "Base", "Base" },
+                dataContexts);
+        }
+
+        private Control CreateTreeViewTemplate(ITemplatedControl parent)
+        {
+            return new ScrollViewer
+            {
+                Template = new ControlTemplate(CreateScrollViewerTemplate),
+                Content = new ItemsPresenter
+                {
+                    Name = "itemsPresenter",
+                    [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty),
+                }
+            };
+        }
+
+        private Control CreateScrollViewerTemplate(ITemplatedControl parent)
+        {
+            return new ScrollContentPresenter
+            {
+                [~ContentPresenter.ContentProperty] = parent.GetObservable(ContentControl.ContentProperty),
+            };
+        }
+
+        private class Item
+        {
+            public Item(string value)
+            {
+                Value = value;
+            }
+
+            public string Value { get; }
+        }
+    }
+}