It's a known issue for WPF. You are, afterall, working with a beta.

>I create a simple WPF form with EF data and build. So far so good it works. Then I make a change (any simple change) and try to rebuild and run. But it fails saying that it cannot copy bin\debug\WpfAndEF.exe from obj\debug\WpfAndEF.exe because it is in use. It is not in use.
>If I restart VS I can build and run new one.
>
>Windows 7 x64 RC, VS2010 Public Beta1 ( I knew that drop downs at top was not a good idea to specify version, OS etc:). Does it happen to you too or is it some bug I encountered?
>Cetin