title: xamarin.forms project add refrence myproj.uwp.exe throw exception
body: <p><a href="https://i.stack.imgur.com/TzxFp.png" rel="nofollow noreferrer">when I add refrence xfproj.uwp,error occur</a></p>
  
  <p><a href="https://i.stack.imgur.com/Z5Kxm.png" rel="nofollow noreferrer">xfproj project,debug or build is ok</a></p>
  
  <p><a href="https://i.stack.imgur.com/Ba5CX.png" rel="nofollow noreferrer">xfproj output,I add reference to XFsecond.uwp project</a></p>
  
  <p>when I add refrence (xfproj.Android) to xfsecond.android ,or xfproj.iOS to xfsecond.iOS, it would be fine.  thx ,who can tell me.</p>