WPF Sentinel objects and how to check for an internal type

Question

As some of you have discovered, a new feature (?) appeared WPF 4, where the data binding engine may pass your custom control instances of the class MS.Internal.Named

Answer 1

This one?

var disconnectedItem = typeof(System.Windows.Data.BindingExpressionBase)
    .GetField("DisconnectedItem", BindingFlags.Static | BindingFlags.NonPublic)
    .GetValue(null);

Answer 2

In .NET 4.5, you can now compare against BindingOperations.DisconnectedSource.