Added Design.DataContext

src/Perspex.Application/Designer/Design.cs

@@ -25,7 +25,7 @@ namespace Perspex
         }
 
         public static readonly PerspexProperty<double> WidthProperty = PerspexProperty
-            .RegisterAttached<TopLevel, double>("Width", typeof (Design));
+    .RegisterAttached<TopLevel, double>("Width", typeof(Design));
 
         public static void SetWidth(TopLevel topLevel, double value)
         {
@@ -34,13 +34,27 @@ namespace Perspex
 
         public static double GetWidth(TopLevel topLevel)
         {
-            return (double) topLevel.GetValue(WidthProperty);
+            return (double)topLevel.GetValue(WidthProperty);
+        }
+
+        public static readonly PerspexProperty<object> DataContextProperty = PerspexProperty
+            .RegisterAttached<TopLevel, object>("DataContext", typeof (Design));
+
+        public static void SetDataContext(TopLevel topLevel, object value)
+        {
+            topLevel.SetValue(DataContextProperty, value);
+        }
+
+        public static object GetDataContext(TopLevel topLevel)
+        {
+            return topLevel.GetValue(DataContextProperty);
         }
 
         static Design()
         {
             WidthProperty.Changed.Subscribe(OnChanged);
             HeightProperty.Changed.Subscribe(OnChanged);
+            DataContextProperty.Changed.Subscribe(OnChanged);
         }
 
         static void OnChanged(PerspexPropertyChangedEventArgs args)
@@ -51,6 +65,8 @@ namespace Perspex
                 ((TopLevel) args.Sender).Width = (double) args.NewValue;
             if (args.Property == HeightProperty)
                 ((TopLevel)args.Sender).Height = (double)args.NewValue;
+            if (args.Property == DataContextProperty)
+                ((TopLevel) args.Sender).DataContext = args.NewValue;
         }
     }
 }