Allow binding to plain IObservables.

Perspex.Base/Binding.cs

@@ -6,6 +6,9 @@
 
 namespace Perspex
 {
+    using System;
+    using System.Reactive.Linq;
+
     public enum BindingMode
     {
         Default,
@@ -15,7 +18,7 @@ namespace Perspex
         OneWayToSource,
     }
 
-    public struct Binding
+    public class Binding : IObservable<object>
     {
         public BindingMode Mode
         {
@@ -51,6 +54,11 @@ namespace Perspex
             return binding.WithMode(BindingMode.TwoWay);
         }
 
+        public IDisposable Subscribe(IObserver<object> observer)
+        {
+            return this.Source.GetObservable(Property).Subscribe(observer);
+        }
+
         public Binding WithMode(BindingMode mode)
         {
             this.Mode = mode;

Perspex.Base/PerspexObject.cs

@@ -143,7 +143,7 @@ namespace Perspex
         /// Gets or sets a binding for a <see cref="PerspexProperty"/>.
         /// </summary>
         /// <param name="binding">The binding information.</param>
-        public Binding this[Binding binding]
+        public IObservable<object> this[Binding binding]
         {
             get
             {
@@ -161,21 +161,27 @@ namespace Perspex
                 BindingMode mode = (binding.Mode == BindingMode.Default) ? 
                     binding.Property.DefaultBindingMode : 
                     binding.Mode;
+                Binding sourceBinding = value as Binding;
+
+                if (sourceBinding == null && mode != BindingMode.OneWay)
+                {
+                    throw new InvalidOperationException("Can only bind OneWay to plain IObservable.");
+                }
 
                 switch (mode)
                 {
                     case BindingMode.Default:
                     case BindingMode.OneWay:
-                        this.Bind(binding.Property, value.Source.GetObservable(value.Property), binding.Priority);
+                        this.Bind(binding.Property, value, binding.Priority);
                         break;
                     case BindingMode.OneTime:
-                        this.SetValue(binding.Property, value.Source.GetValue(value.Property));
+                        this.SetValue(binding.Property, sourceBinding.Source.GetValue(sourceBinding.Property));
                         break;
                     case BindingMode.OneWayToSource:
-                        value.Source.Bind(value.Property, this.GetObservable(binding.Property), binding.Priority);
+                        sourceBinding.Source.Bind(sourceBinding.Property, this.GetObservable(binding.Property), binding.Priority);
                         break;
                     case BindingMode.TwoWay:
-                        this.BindTwoWay(binding.Property, value.Source, value.Property);
+                        this.BindTwoWay(binding.Property, sourceBinding.Source, sourceBinding.Property);
                         break;
                 }
             }

packages/repositories.config

@@ -4,6 +4,7 @@
   <repository path="..\Perspex.Base\packages.config" />
   <repository path="..\Perspex.Controls.UnitTests\packages.config" />
   <repository path="..\Perspex.Controls\packages.config" />
+  <repository path="..\Perspex.Diagnostics\packages.config" />
   <repository path="..\Perspex.Direct2D1.RenderTests\packages.config" />
   <repository path="..\Perspex.Direct2D1\packages.config" />
   <repository path="..\Perspex.Input\packages.config" />
@@ -16,6 +17,5 @@
   <repository path="..\Perspex.Themes.Default\packages.config" />
   <repository path="..\Perspex.UnitTests\packages.config" />
   <repository path="..\Perspex.Windows\packages.config" />
-  <repository path="..\Perspex\packages.config" />
   <repository path="..\TestApplication\packages.config" />
 </repositories>