title: Change Target Framework from 4.5 to 4.0
body: <p>I am trying to change the target framework from 4.5 to 4.0, I have changed the target framework on all of my projects and I have created a testing build with VS2015. 
  <br> <br>
  I am trying to run the app in WIN7 with .NET 4.0 installed but the app crashes and the errors are System.IO.FileLoadException for mscorlib.dll and PresentationFramework.dll
  <br> <br>
  Does anyone know how to fix it?</p>
  
  <p><em>More info</em> 
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  I have tried also:</p>
  
  <ol>
  <li>to build with vs2012 but I cannot use vs2010 because I am using async from BCL package</li>
  <li>to create new solution with new projects to target from the start 4.0 framework.</li>
  </ol>