title: How to implement INotifyDataErrorInfo in WPF 4.5?
body: <p>I realized that appears this interface in .NET Framework 4.5</p>
  
  <p>I was looking first for about how to implemented in Silverlight (I can imagine that it's implemented in the same way), but I can't find a compact demo of this new interface. Is it possible to show how can I use it?</p>
  
  <p>I really want to find a small demo to understand it</p>