Removed Scrollbar binding workaround.

Binding system now handles this. Added unit tests to ensure it works
property.

Perspex.Controls/Primitives/ScrollBar.cs

@@ -82,21 +82,6 @@ namespace Perspex.Controls.Primitives
             return base.MeasureOverride(availableSize);
         }
 
-        /// <inheritdoc/>
-        protected override void OnTemplateApplied()
-        {
-            base.OnTemplateApplied();
-
-            // Binding between this.Value and track.Value must be done explicitly like this rather
-            // than using standard bindings as it shouldn't be able to to be overridden by binding
-            // e.g. ScrollBar.Value.
-            // TODO: This is probably no longer true. Test and use a standard 2 way binding if
-            // possible.
-            var track = this.GetTemplateChild<Track>("track");
-            track.GetObservable(ValueProperty).Subscribe(x => this.Value = x);
-            this.GetObservable(ValueProperty).Subscribe(x => track.Value = x);
-        }
-
         /// <summary>
         /// Calculates whether the scrollbar should be visible.
         /// </summary>

Perspex.Themes.Default/ScrollBarStyle.cs

@@ -67,10 +67,11 @@ namespace Perspex.Themes.Default
                 Child = new Track
                 {
                     Name = "track",
-                    [~Track.MinimumProperty] = control[~ScrollBar.MinimumProperty],
-                    [~Track.MaximumProperty] = control[~ScrollBar.MaximumProperty],
-                    [~Track.ViewportSizeProperty] = control[~ScrollBar.ViewportSizeProperty],
-                    [~Track.OrientationProperty] = control[~ScrollBar.OrientationProperty],
+                    [!Track.MinimumProperty] = control[!ScrollBar.MinimumProperty],
+                    [!Track.MaximumProperty] = control[!ScrollBar.MaximumProperty],
+                    [!!Track.ValueProperty] = control[!!ScrollBar.ValueProperty],
+                    [!Track.ViewportSizeProperty] = control[!ScrollBar.ViewportSizeProperty],
+                    [!Track.OrientationProperty] = control[!ScrollBar.OrientationProperty],
                     Thumb = new Thumb
                     {
                         Name = "thumb",

Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj

@@ -96,6 +96,7 @@
     <Compile Include="DropDownTests.cs" />
     <Compile Include="Presenters\ItemsPresenterTests.cs" />
     <Compile Include="Presenters\ScrollContentPresenterTests.cs" />
+    <Compile Include="Primitives\ScrollBarTests.cs" />
     <Compile Include="Primitives\RangeBaseTests.cs" />
     <Compile Include="ScrollViewerTests.cs" />
     <Compile Include="Primitives\SelectingItemsControlTests.cs" />

Tests/Perspex.Controls.UnitTests/Primitives/RangeBaseTests.cs

@@ -6,8 +6,8 @@
 
 namespace Perspex.Controls.UnitTests.Primitives
 {
-    using Perspex.Controls.Primitives;
     using System;
+    using Perspex.Controls.Primitives;
     using Xunit;
 
     public class RangeBaseTests

Tests/Perspex.Controls.UnitTests/Primitives/ScrollBarTests.cs

@@ -0,0 +1,92 @@
+// -----------------------------------------------------------------------
+// <copyright file="ScrollBarTests.cs" company="Steven Kirk">
+// Copyright 2015 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls.UnitTests.Primitives
+{
+    using System;
+    using Perspex.Controls.Primitives;
+    using Perspex.Controls.Templates;
+    using Perspex.Media;
+    using Xunit;
+
+    public class ScrollBarTests
+    {
+        [Fact]
+        public void Setting_Value_Should_Update_Track_Value()
+        {
+            var target = new ScrollBar
+            {
+                Template = ControlTemplate.Create<ScrollBar>(Template),
+            };
+
+            target.ApplyTemplate();
+            var track = target.GetTemplateChild<Track>("track");
+            target.Value = 50;
+
+            Assert.Equal(track.Value, 50);
+        }
+
+        [Fact]
+        public void Setting_Track_Value_Should_Update_Value()
+        {
+            var target = new ScrollBar
+            {
+                Template = ControlTemplate.Create<ScrollBar>(Template),
+            };
+
+            target.ApplyTemplate();
+            var track = target.GetTemplateChild<Track>("track");
+            track.Value = 50;
+
+            Assert.Equal(target.Value, 50);
+        }
+
+        [Fact]
+        public void Setting_Track_Value_After_Setting_Value_Should_Update_Value()
+        {
+            var target = new ScrollBar
+            {
+                Template = ControlTemplate.Create<ScrollBar>(Template),
+            };
+
+            target.ApplyTemplate();
+
+            var track = target.GetTemplateChild<Track>("track");
+            target.Value = 25;
+            track.Value = 50;
+
+            Assert.Equal(target.Value, 50);
+        }
+
+        private static Control Template(ScrollBar control)
+        {
+            return new Border
+            {
+                Child = new Track
+                {
+                    Name = "track",
+                    [!Track.MinimumProperty] = control[!ScrollBar.MinimumProperty],
+                    [!Track.MaximumProperty] = control[!ScrollBar.MaximumProperty],
+                    [!!Track.ValueProperty] = control[!!ScrollBar.ValueProperty],
+                    [!Track.ViewportSizeProperty] = control[!ScrollBar.ViewportSizeProperty],
+                    [!Track.OrientationProperty] = control[!ScrollBar.OrientationProperty],
+                    Thumb = new Thumb
+                    {
+                        Template = ControlTemplate.Create<Thumb>(ThumbTemplate),
+                    },
+                },
+            };
+        }
+
+        private static Control ThumbTemplate(Thumb control)
+        {
+            return new Border
+            {
+                Background = Brushes.Gray,
+            };
+        }
+    }
+}