title: Can an application target to both 3.5 and 4.5 .Net version?
body: <p>I write a WPF app, that all source code compatible with both .NET 3.5 and 4.5. That mean if I change .NET target in the Properties to either 3.5 or 4.5, it will complie and run well without any error.<br>
  I wonder there is anyway to my my app file can run on both 3.5 and 4.5 .NET pc (example: Windows 7 and Windows 8.1), without complie 2 version for each .NET? Thank!</p>
  
  <p><strong>Edit:</strong><br>
  <em>When I copy the .NET 3.5 application in question to a Windows 8.1 pc, Windows refuse to run my app, and require I install .NET 3.5. So if only complie with .NET 3.5, it dont make app can run in .NET 4.5 pc.</em></p>