title: MEF CS0234: The type or namespace name 'Composition' does not exist in the namespace 'System.ComponentModel' (are you missing an assembly reference?)
body: <p>I have added in ComponentModel.Composition; assembly .But  showing this error for </p>
  
  <p>using System.ComponentModel.Composition;</p>
  
  <p>and reference for the assembely</p>
  
  <p>still gets the error</p>
  
  <p><strong>CS0234: The type or namespace name 'Composition' does not exist in the namespace 'System.ComponentModel' (are you missing an assembly reference?)</strong></p>