title: Properties does not exist: System.Windows.Interactivity?
body: <p>I have C#/WPF that has a persistent problem loading/resolving the System.Windows.Interactivity
  I am using Visual Studio 2010 as my editor and already installed Blend 4 + Blend 4 SDK,</p>
  <blockquote>
  <p>......</p>
  <p>xmlns:i=&quot;clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity&quot;&gt;</p>
  </blockquote>
  <p>Why still return result Assembly was not found? Like my class library CustomBehaviorLibrary was missing?</p>