BindingProxy.cs

using System;
using System.Windows;

namespace Ldar.Chateau.Prism.Resources
{
   /// <summary>
   /// Some markup elements (DataGridTemplateColumn and telerik:GridViewDataColumn.Header, for example)
   /// are not part of the visual or logical tree, and therefore has no binding ancestor (or any 
   /// ancestor) so the RelativeSource doesn't work. When you need RelativeSource for binding,
   /// we instead have to bind to a local proxy.
   /// http://stackoverflow.com/questions/15494226/cannot-find-source-for-binding-with-reference-relativesource-findancestor
   /// </summary>
   public class BindingProxy : Freezable
   {
      protected override Freezable CreateInstanceCore()
      {
         return new BindingProxy();
      }

      public object Data
      {
         get { return (object)GetValue(DataProperty); }
         set { SetValue(DataProperty, value); }
      }

      public static readonly DependencyProperty DataProperty =
          DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
   }
}