TreeView work in progress...

Perspex.UnitTests/PerspexObjectTests.cs

@@ -161,6 +161,15 @@ namespace Perspex.UnitTests
             target.SetValue(Class2.BarProperty, "invalid");
         }
 
+        [TestMethod]
+        [ExpectedException(typeof(InvalidOperationException))]
+        public void SetValue_Throws_Exception_For_Invalid_Value_Type()
+        {
+            Class1 target = new Class1();
+
+            target.SetValue(Class1.FooProperty, 123);
+        }
+
         [TestMethod]
         public void GetObservable_Returns_Initial_Value()
         {
@@ -271,7 +280,7 @@ namespace Perspex.UnitTests
         }
 
         [TestMethod]
-        public void Binding_Sets_Current_Value()
+        public void Bind_Sets_Current_Value()
         {
             Class1 target = new Class1();
             Class1 source = new Class1();
@@ -283,7 +292,7 @@ namespace Perspex.UnitTests
         }
 
         [TestMethod]
-        public void Binding_NonGeneric_Sets_Current_Value()
+        public void Bind_NonGeneric_Sets_Current_Value()
         {
             Class1 target = new Class1();
             Class1 source = new Class1();
@@ -295,7 +304,7 @@ namespace Perspex.UnitTests
         }
 
         [TestMethod]
-        public void Binding_Sets_Subsequent_Value()
+        public void Bind_Sets_Subsequent_Value()
         {
             Class1 target = new Class1();
             Class1 source = new Class1();
@@ -322,7 +331,7 @@ namespace Perspex.UnitTests
         }
 
         [TestMethod]
-        public void Binding_Doesnt_Set_Value_After_Reset()
+        public void Bind_Doesnt_Set_Value_After_Reset()
         {
             Class1 target = new Class1();
             Class1 source = new Class1();
@@ -335,6 +344,15 @@ namespace Perspex.UnitTests
             Assert.AreEqual("reset", target.GetValue(Class1.FooProperty));
         }
 
+        [TestMethod]
+        [ExpectedException(typeof(InvalidOperationException))]
+        public void Bind_Throws_Exception_For_Invalid_Value_Type()
+        {
+            Class1 target = new Class1();
+
+            target.Bind((PerspexProperty)Class1.FooProperty, Observable.Return((object)123));
+        }
+
         [TestMethod]
         public void Setting_UnsetValue_Reverts_To_Default_Value()
         {

Perspex.UnitTests/PriorityValueTEsts.cs

@@ -19,7 +19,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Initial_Value_Should_Be_UnsetValue()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             Assert.AreSame(PerspexProperty.UnsetValue, target.Value);
         }
@@ -27,7 +27,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void First_Binding_Sets_Value()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             target.Add(this.Single("foo"), 0);
 
@@ -37,7 +37,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Changing_Binding_Should_Set_Value()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<string>("foo");
 
             target.Add(subject, 0);
@@ -49,7 +49,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Binding_With_Lower_Priority_Has_Precedence()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             target.Add(this.Single("foo"), 1);
             target.Add(this.Single("bar"), 0);
@@ -61,7 +61,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Later_Binding_With_Same_Priority_Should_Take_Precedence()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             target.Add(this.Single("foo"), 1);
             target.Add(this.Single("bar"), 0);
@@ -74,7 +74,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Changing_Binding_With_Lower_Priority_Should_Set_Not_Value()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<string>("bar");
 
             target.Add(this.Single("foo"), 0);
@@ -87,7 +87,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void UnsetValue_Should_Fall_Back_To_Next_Binding()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<object>("bar");
 
             target.Add(subject, 0);
@@ -103,7 +103,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Adding_Value_Should_Call_OnNext()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             bool called = false;
 
             target.Changed.Subscribe(value => called = (value.Item1 == PerspexProperty.UnsetValue && (string)value.Item2 == "foo"));
@@ -115,7 +115,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Changing_Value_Should_Call_OnNext()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<object>("foo");
             bool called = false;
 
@@ -129,7 +129,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Disposing_A_Binding_Should_Revert_To_Next_Value()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             target.Add(this.Single("foo"), 0);
             var disposable = target.Add(this.Single("bar"), 0);
@@ -142,7 +142,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Disposing_A_Binding_Should_Remove_BindingEntry()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
 
             target.Add(this.Single("foo"), 0);
             var disposable = target.Add(this.Single("bar"), 0);
@@ -155,7 +155,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Completing_A_Binding_Should_Revert_To_Next_Value()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<object>("bar");
 
             target.Add(this.Single("foo"), 0);
@@ -169,7 +169,7 @@ namespace Perspex.UnitTests
         [TestMethod]
         public void Completing_A_Binding_Should_Remove_BindingEntry()
         {
-            var target = new PriorityValue();
+            var target = new PriorityValue("Test", typeof(string));
             var subject = new BehaviorSubject<object>("bar");
 
             target.Add(this.Single("foo"), 0);

Perspex/Controls/DataTemplate.cs

@@ -20,7 +20,7 @@ namespace Perspex.Controls
         }
 
         public DataTemplate(Type type, Func<object, Control> build)
-            : this(o => type.GetTypeInfo().IsAssignableFrom(o.GetType().GetTypeInfo()), build)
+            : this(o => IsInstance(o, type), build)
         {
         }
 
@@ -33,6 +33,11 @@ namespace Perspex.Controls
             this.Build = build;
         }
 
+        public static bool IsInstance(object o, Type t)
+        {
+            return t.GetTypeInfo().IsAssignableFrom(o.GetType().GetTypeInfo());
+        }
+
         public Func<object, bool> Match { get; private set; }
 
         public Func<object, Control> Build { get; private set; }

Perspex/Controls/HeaderedItemsControl.cs

@@ -0,0 +1,25 @@
+// -----------------------------------------------------------------------
+// <copyright file="HeaderedItemsControl.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    using System;
+    using System.Collections;
+    using System.Linq;
+    using System.Reactive.Linq;
+
+    public class HeaderedItemsControl : ItemsControl
+    {
+        public static readonly PerspexProperty<object> HeaderProperty =
+            HeaderedContentControl.HeaderProperty.AddOwner<HeaderedItemsControl>();
+
+        public object Header
+        {
+            get { return this.GetValue(HeaderProperty); }
+            set { this.SetValue(HeaderProperty, value); }
+        }
+    }
+}

Perspex/Controls/ItemsControl.cs

@@ -21,9 +21,6 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<ItemsPanelTemplate> ItemsPanelProperty =
             PerspexProperty.Register<ItemsControl, ItemsPanelTemplate>("ItemsPanel", defaultValue: DefaultPanel);
 
-        public static readonly PerspexProperty<DataTemplate> ItemTemplateProperty =
-            PerspexProperty.Register<ItemsControl, DataTemplate>("ItemTemplate");
-
         private Dictionary<object, Control> itemControls = new Dictionary<object, Control>();
 
         public IEnumerable Items
@@ -38,12 +35,6 @@ namespace Perspex.Controls
             set { this.SetValue(ItemsPanelProperty, value); }
         }
 
-        public DataTemplate ItemTemplate
-        {
-            get { return this.GetValue(ItemTemplateProperty); }
-            set { this.SetValue(ItemTemplateProperty, value); }
-        }
-
         public Control GetControlForItem(object item)
         {
             Control result;
@@ -65,21 +56,7 @@ namespace Perspex.Controls
 
         protected virtual Control CreateItemControlOverride(object item)
         {
-            Control control = item as Control;
+            return (item as Control) ?? this.GetDataTemplate(item).Build(item);
-            DataTemplate template = this.ItemTemplate;
-
-            if (control != null)
-            {
-                return control;
-            }
-            else if (template != null)
-            {
-                return template.Build(item);
-            }
-            else
-            {
-                return this.GetDataTemplate(item).Build(item);
-            }
         }
     }
 }

Perspex/Controls/ItemsPresenter.cs

@@ -20,9 +20,6 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<ItemsPanelTemplate> ItemsPanelProperty =
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
-        public static readonly PerspexProperty<DataTemplate> ItemTemplateProperty =
-            ItemsControl.ItemTemplateProperty.AddOwner<ItemsPresenter>();
-
         private Panel panel;
 
         public ItemsPresenter()
@@ -42,12 +39,6 @@ namespace Perspex.Controls
             set { this.SetValue(ItemsPanelProperty, value); }
         }
 
-        public DataTemplate ItemTemplate
-        {
-            get { return this.GetValue(ItemTemplateProperty); }
-            set { this.SetValue(ItemTemplateProperty, value); }
-        }
-
         IEnumerable<IVisual> IVisual.ExistingVisualChildren
         {
             get { return Enumerable.Repeat(this.panel, this.panel != null ? 1 : 0); }

Perspex/Controls/TabStrip.cs

@@ -14,13 +14,9 @@ namespace Perspex.Controls
         private static readonly ItemsPanelTemplate PanelTemplate = new ItemsPanelTemplate(
             () => new StackPanel());
 
-        private static readonly DataTemplate TabTemplate = new DataTemplate(
-            o => new TabItem { Content = o });
-
         static TabStrip()
         {
             ItemsPanelProperty.OverrideDefaultValue(typeof(TabStrip), PanelTemplate);
-            ItemTemplateProperty.OverrideDefaultValue(typeof(TabStrip), TabTemplate);
         }
 
         public TabStrip()
@@ -37,7 +33,7 @@ namespace Perspex.Controls
             {
                 result = new TabItem
                 {
-                    Content = item,
+                    Content = this.GetDataTemplate(item).Build(item),
                 };
             }
 

Perspex/Controls/TreeDataTemplate.cs

@@ -0,0 +1,58 @@
+// -----------------------------------------------------------------------
+// <copyright file="TreeDataTemplate.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    using System;
+    using System.Collections;
+
+    public class TreeDataTemplate : DataTemplate
+    {
+        public TreeDataTemplate(
+            Func<object, Control> build, 
+            Func<object, IEnumerable> itemsSelector)
+            : this(o => true, build, itemsSelector)
+        {
+        }
+
+        public TreeDataTemplate(
+            Type type, 
+            Func<object, Control> build,
+            Func<object, IEnumerable> itemsSelector)
+            : this(o => IsInstance(o, type), build, itemsSelector)
+        {
+        }
+
+        public TreeDataTemplate(
+            Func<object, bool> match, 
+            Func<object, Control> build,
+            Func<object, IEnumerable> itemsSelector)
+            : base(match, build)
+        {
+            this.ItemsSelector = itemsSelector;
+        }
+
+        public Func<object, IEnumerable> ItemsSelector { get; private set; }
+    }
+
+    public class TreeDataTemplate<T> : TreeDataTemplate
+    {
+        public TreeDataTemplate(
+            Func<object, Control> build,
+            Func<T, IEnumerable> itemsSelector)
+            : base(typeof(T), o => build((T)o), o => itemsSelector((T)o))
+        {
+        }
+
+        public TreeDataTemplate(
+            Func<T, bool> match, 
+            Func<T, Control> build,
+            Func<T, IEnumerable> itemsSelector)
+            : base(o => (o is T) ? match((T)o) : false, o => build((T)o), o => itemsSelector((T)o))
+        {
+        }
+    }
+}

Perspex/Controls/TreeView.cs

@@ -0,0 +1,47 @@
+// -----------------------------------------------------------------------
+// <copyright file="TreeView.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    using System;
+    using System.Collections;
+    using System.Linq;
+    using System.Reactive.Linq;
+
+    public class TreeView : SelectingItemsControl
+    {
+        protected override Control CreateItemControlOverride(object item)
+        {
+            TreeViewItem result = item as TreeViewItem;
+
+            if (result == null)
+            {
+                TreeDataTemplate template = this.GetTreeDataTemplate(item);
+
+                result = new TreeViewItem
+                {
+                    Header = template.Build(item),
+                    Items = template.ItemsSelector(item),
+                };
+            }
+
+            return result;
+        }
+
+        private TreeDataTemplate GetTreeDataTemplate(object item)
+        {
+            DataTemplate template = this.GetDataTemplate(item);
+            TreeDataTemplate treeTemplate = template as TreeDataTemplate;
+
+            if (treeTemplate == null)
+            {
+                treeTemplate = new TreeDataTemplate(template.Build, x => null);
+            }
+
+            return treeTemplate;
+        }
+    }
+}

Perspex/Controls/TreeViewItem.cs

@@ -0,0 +1,17 @@
+// -----------------------------------------------------------------------
+// <copyright file="TreeViewItem.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls
+{
+    using System;
+    using System.Collections;
+    using System.Linq;
+    using System.Reactive.Linq;
+
+    public class TreeViewItem : HeaderedItemsControl
+    {
+    }
+}

Perspex/Perspex.csproj

@@ -70,9 +70,13 @@
   <ItemGroup>
     <Compile Include="Application.cs" />
     <Compile Include="BindingExtensions.cs" />
+    <Compile Include="Controls\TreeDataTemplate.cs" />
     <Compile Include="Controls\HeaderedContentControl.cs" />
     <Compile Include="Controls\Controls.cs" />
     <Compile Include="Controls\SelectingItemsControl.cs" />
+    <Compile Include="Controls\HeaderedItemsControl.cs" />
+    <Compile Include="Controls\TreeViewItem.cs" />
+    <Compile Include="Controls\TreeView.cs" />
     <Compile Include="Controls\TabItem.cs" />
     <Compile Include="Controls\TabControl.cs" />
     <Compile Include="Controls\TabStrip.cs" />
@@ -135,6 +139,8 @@
     <Compile Include="Media\Geometry.cs" />
     <Compile Include="Media\Stretch.cs" />
     <Compile Include="Themes\Default\ContentControlStyle.cs" />
+    <Compile Include="Themes\Default\TreeViewItemStyle.cs" />
+    <Compile Include="Themes\Default\TreeViewStyle.cs" />
     <Compile Include="Themes\Default\ItemsControlStyle.cs" />
     <Compile Include="Themes\Default\TabItemStyle.cs" />
     <Compile Include="Themes\Default\TabControlStyle.cs" />

Perspex/PerspexObject.cs

@@ -43,6 +43,11 @@ namespace Perspex
         /// A style binding.
         /// </summary>
         Style,
+
+        /// <summary>
+        /// The binding is uninitialized.
+        /// </summary>
+        Unset = int.MaxValue,
     }
 
     /// <summary>
@@ -200,7 +205,7 @@ namespace Perspex
         }
 
         /// <summary>
-        /// Clears a <see cref="PerspexProperty"/> value, including its binding.
+        /// Clears a <see cref="PerspexProperty"/>'s local value.
         /// </summary>
         /// <param name="property">The property.</param>
         public void ClearValue(PerspexProperty property)
@@ -394,6 +399,15 @@ namespace Perspex
                     this.GetType()));
             }
 
+            if (!PriorityValue.IsValidValue(value, property.PropertyType))
+            {
+                throw new InvalidOperationException(string.Format(
+                    "Invalid value for Property '{0}': {1} ({2})",
+                    property.Name,
+                    value,
+                    value.GetType().FullName));
+            }
+
             if (!this.values.TryGetValue(property, out v))
             {
                 if (value == PerspexProperty.UnsetValue)
@@ -493,7 +507,7 @@ namespace Perspex
 
         private PriorityValue CreatePriorityValue(PerspexProperty property)
         {
-            PriorityValue result = new PriorityValue();
+            PriorityValue result = new PriorityValue(property.Name, property.PropertyType);
 
             result.Changed.Subscribe(x =>
             {

Perspex/PerspexProperty.cs

@@ -25,7 +25,7 @@ namespace Perspex
         /// <summary>
         /// Represents an unset property value.
         /// </summary>
-        public static readonly object UnsetValue = new object();
+        public static readonly object UnsetValue = new Unset();
 
         /// <summary>
         /// The default values for the property, by type.
@@ -259,6 +259,14 @@ namespace Perspex
                 private set;
             }
         }
+
+        private class Unset
+        {
+            public override string ToString()
+            {
+                return "{Unset}";
+            }
+        }
     }
 
     /// <summary>

Perspex/PriorityValue.cs

@@ -10,6 +10,7 @@ namespace Perspex
     using System.Collections.Generic;
     using System.Reactive.Disposables;
     using System.Reactive.Subjects;
+    using System.Reflection;
 
     /// <summary>
     /// Maintains a list of prioritised bindings together with a current value.
@@ -25,6 +26,16 @@ namespace Perspex
     /// </remarks>
     public class PriorityValue
     {
+        /// <summary>
+        /// The name of the property.
+        /// </summary>
+        private string name;
+
+        /// <summary>
+        /// The value type.
+        /// </summary>
+        private Type valueType;
+
         /// <summary>
         /// The currently registered binding entries.
         /// </summary>
@@ -43,8 +54,12 @@ namespace Perspex
         /// <summary>
         /// Initializes a new instance of the <see cref="PriorityValue"/> class.
         /// </summary>
-        public PriorityValue()
+        /// <param name="name">The name of the property.</param>
+        /// <param name="valueType">The value type.</param>
+        public PriorityValue(string name, Type valueType)
         {
+            this.name = name;
+            this.valueType = valueType;
             this.value = PerspexProperty.UnsetValue;
             this.ValuePriority = int.MaxValue;
         }
@@ -74,6 +89,39 @@ namespace Perspex
             private set;
         }
 
+        /// <summary>
+        /// Checks whether a value is valid for a type.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="propertyType"></param>
+        /// <returns></returns>
+        public static bool IsValidValue(object value, Type propertyType)
+        {
+            TypeInfo type = propertyType.GetTypeInfo();
+
+            if (value == PerspexProperty.UnsetValue)
+            {
+                return true;
+            }
+            else if (value == null)
+            {
+                if (type.IsValueType && 
+                    (!type.IsGenericType || !(type.GetGenericTypeDefinition() == typeof(Nullable<>))))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!type.IsAssignableFrom(value.GetType().GetTypeInfo()))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
         /// <summary>
         /// Adds a new binding.
         /// </summary>
@@ -218,6 +266,15 @@ namespace Perspex
         /// <param name="priority">The priority of the binding which produced the value.</param>
         private void SetValue(object value, int priority)
         {
+            if (!IsValidValue(value, this.valueType))
+            {
+                throw new InvalidOperationException(string.Format(
+                    "Invalid value for Property '{0}': {1} ({2})",
+                    this.name,
+                    value,
+                    value.GetType().FullName));
+            }
+
             object old = this.value;
 
             this.ValuePriority = priority;

Perspex/Themes/Default/DefaultTheme.cs

@@ -20,6 +20,8 @@ namespace Perspex.Themes.Default
             this.Add(new TabItemStyle());
             this.Add(new TabStripStyle());
             this.Add(new TextBoxStyle());
+            this.Add(new TreeViewStyle());
+            this.Add(new TreeViewItemStyle());
         }
     }
 }

Perspex/Themes/Default/ItemsControlStyle.cs

@@ -32,7 +32,6 @@ namespace Perspex.Themes.Default
             {
                 [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                 [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
-                [~ItemsPresenter.ItemTemplateProperty] = control[~ItemsControl.ItemTemplateProperty],
             };
         }
     }

Perspex/Themes/Default/TabStripStyle.cs

@@ -40,7 +40,6 @@ namespace Perspex.Themes.Default
             {
                 [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                 [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
-                [~ItemsPresenter.ItemTemplateProperty] = control[~ItemsControl.ItemTemplateProperty],
             };
         }
     }

Perspex/Themes/Default/TreeViewItemStyle.cs

@@ -0,0 +1,49 @@
+// -----------------------------------------------------------------------
+// <copyright file="TreeViewItemStyle.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Themes.Default
+{
+    using System.Linq;
+    using Perspex.Controls;
+    using Perspex.Styling;
+
+    public class TreeViewItemStyle : Styles
+    {
+        public TreeViewItemStyle()
+        {
+            this.AddRange(new[]
+            {
+                new Style(x => x.OfType<TreeViewItem>())
+                {
+                    Setters = new[]
+                    {
+                        new Setter(Button.TemplateProperty, ControlTemplate.Create<TreeViewItem>(this.Template)),
+                    },
+                },
+            });
+        }
+
+        private Control Template(TreeViewItem control)
+        {
+            return new StackPanel
+            {
+                Children = new Controls
+                {
+                    new ContentPresenter
+                    {
+                        [~ContentPresenter.ContentProperty] = control[~TreeViewItem.HeaderProperty],
+                    },
+                    new ItemsPresenter
+                    {
+                        Margin = new Thickness(13, 0, 0, 0),
+                        [~ItemsPresenter.ItemsProperty] = control[~TreeViewItem.ItemsProperty],
+                        [~ItemsPresenter.ItemsPanelProperty] = control[~TreeViewItem.ItemsPanelProperty],
+                    }
+                }
+            };
+        }
+    }
+}

Perspex/Themes/Default/TreeViewStyle.cs

@@ -0,0 +1,38 @@
+// -----------------------------------------------------------------------
+// <copyright file="TreeViewStyle.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Themes.Default
+{
+    using System.Linq;
+    using Perspex.Controls;
+    using Perspex.Styling;
+
+    public class TreeViewStyle : Styles
+    {
+        public TreeViewStyle()
+        {
+            this.AddRange(new[]
+            {
+                new Style(x => x.OfType<TreeView>())
+                {
+                    Setters = new[]
+                    {
+                        new Setter(Button.TemplateProperty, ControlTemplate.Create<TreeView>(this.Template)),
+                    },
+                },
+            });
+        }
+
+        private Control Template(TreeView control)
+        {
+            return new ItemsPresenter
+            {
+                [~ItemsPresenter.ItemsProperty] = control[~TreeView.ItemsProperty],
+                [~ItemsPresenter.ItemsPanelProperty] = control[~TreeView.ItemsPanelProperty],
+            };
+        }
+    }
+}

TestApplication/Program.cs

@@ -1,4 +1,6 @@
-using Perspex;
+using System.Collections;
+using System.Collections.Generic;
+using Perspex;
 using Perspex.Controls;
 using Perspex.Layout;
 using Perspex.Media;
@@ -30,74 +32,146 @@ namespace TestApplication
         public string Value { get; set; }
     }
 
+    class Node
+    {
+        public string Name { get; set; }
+        public IEnumerable<Node> Children { get; set; }
+    }
+
     class Program
     {
-        static void Main(string[] args)
+        private static Node[] treeData = new[]
         {
-            App application = new App();
+            new Node
+            {
+                Name = "Root 1",
+                Children = new[]
+                {
+                    new Node
+                    {
+                        Name = "Child 1",
+                    },
+                    new Node
+                    {
+                        Name = "Child 2",
+                        Children = new[]
+                        {
+                            new Node
+                            {
+                                Name = "Grandchild 1",
+                            },
+                            new Node
+                            {
+                                Name = "Grandmaster Flash",
+                            },
+                        }
+                    },
+                    new Node
+                    {
+                        Name = "Child 3",
+                    },
+                }
+            },
+            new Node
+            {
+                Name = "Root 2",
+            },
+        };
 
+        static void Main(string[] args)
+        {
             //Locator.CurrentMutable.Register(() => new TestLogger { Level = LogLevel.Debug } , typeof(ILogger));
 
+            App application = new App
+            {
+                DataTemplates = new DataTemplates
+                {
+                    new TreeDataTemplate<Node>(
+                        x => new TextBlock { Text = x.ToString() },
+                        x => x.Children),
+                },
+            };
+
             Window window = new Window
             {
                 Content = new TabControl
                 {
                     Items = new[]
                     {
+                        //new TabItem
+                        //{
+                        //    Header = "Buttons",
+                        //    Content = new StackPanel
+                        //    {
+                        //        Orientation = Orientation.Vertical,
+                        //        HorizontalAlignment = HorizontalAlignment.Center,
+                        //        VerticalAlignment = VerticalAlignment.Center,
+                        //        Gap = 8,
+                        //        MinWidth = 120,
+                        //        Children = new Controls
+                        //        {
+                        //            new Button
+                        //            {
+                        //                Content = "Button",
+                        //            },
+                        //            new Button
+                        //            {
+                        //                Content = "Button",
+                        //                Background = new SolidColorBrush(0xcc119eda),
+                        //            },
+                        //            new CheckBox
+                        //            {
+                        //                Content = "Checkbox",
+                        //            },
+                        //        }
+                        //    },
+                        //},
+                        //new TabItem
+                        //{
+                        //    Header = "Text",
+                        //    Content = new StackPanel
+                        //    {
+                        //        Orientation = Orientation.Vertical,
+                        //        HorizontalAlignment = HorizontalAlignment.Center,
+                        //        VerticalAlignment = VerticalAlignment.Center,
+                        //        Gap = 8,
+                        //        Width = 120,
+                        //        Children = new Controls
+                        //        {
+                        //            new TextBlock
+                        //            {
+                        //                Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin venenatis dui quis libero suscipit tincidunt.",
+                        //            },
+                        //            new TextBox
+                        //            {
+                        //                Text = "Text Box",
+                        //            },
+                        //        }
+                        //    },
+                        //},
+                        //new TabItem
+                        //{
+                        //    Header = "Images",
+                        //    Content = new StackPanel
+                        //    {
+                        //        Orientation = Orientation.Vertical,
+                        //        HorizontalAlignment = HorizontalAlignment.Center,
+                        //        VerticalAlignment = VerticalAlignment.Center,
+                        //        Gap = 8,
+                        //        Width = 120,
+                        //        Children = new Controls
+                        //        {
+                        //            new Image
+                        //            {
+                        //                Source = new Bitmap("github_icon.png"),
+                        //                Width = 200,
+                        //            },
+                        //        }
+                        //    },
+                        //},
                         new TabItem
                         {
-                            Header = "Buttons",
+                            Header = "Lists",
-                            Content = new StackPanel
-                            {
-                                Orientation = Orientation.Vertical,
-                                HorizontalAlignment = HorizontalAlignment.Center,
-                                VerticalAlignment = VerticalAlignment.Center,
-                                Gap = 8,
-                                MinWidth = 120,
-                                Children = new Controls
-                                {
-                                    new Button
-                                    {
-                                        Content = "Button",
-                                    },
-                                    new Button
-                                    {
-                                        Content = "Button",
-                                        Background = new SolidColorBrush(0xcc119eda),
-                                    },
-                                    new CheckBox
-                                    {
-                                        Content = "Checkbox",
-                                    },
-                                }
-                            },
-                        },
-                        new TabItem
-                        {
-                            Header = "Text",
-                            Content = new StackPanel
-                            {
-                                Orientation = Orientation.Vertical,
-                                HorizontalAlignment = HorizontalAlignment.Center,
-                                VerticalAlignment = VerticalAlignment.Center,
-                                Gap = 8,
-                                Width = 120,
-                                Children = new Controls
-                                {
-                                    new TextBlock
-                                    {
-                                        Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin venenatis dui quis libero suscipit tincidunt.",
-                                    },
-                                    new TextBox
-                                    {
-                                        Text = "Text Box",
-                                    },
-                                }
-                            },
-                        },
-                        new TabItem
-                        {
-                            Header = "Images",
                             Content = new StackPanel
                             {
                                 Orientation = Orientation.Vertical,
@@ -107,10 +181,9 @@ namespace TestApplication
                                 Width = 120,
                                 Children = new Controls
                                 {
-                                    new Image
+                                    new TreeView
                                     {
-                                        Source = new Bitmap("github_icon.png"),
+                                        Items = treeData,
-                                        Width = 200,
                                     },
                                 }
                             },