title: Binary Format of a Custom Attribute error adding microsoft.bcl.async
body: <p>I have a wpf project, compiled as x86 code for framework 4.5, and as part of the migration process of some code to this project I have to add the <strong>microsoft.bcl.async</strong> package.<br>
  If I add this package and start compile I receive this error message <strong>'Binary format of the specified custom attribute was invalid.'</strong> and if I remove the package I can compile again.<br>
  Am I missing something?</p>