Visual Studio 2010 Build Fails to File Copy Error

Question

I'm building a project in Visual Studio 2010 and the build fails because it cannot copy the assemblyname.dll file from obj to bin folder. The exact error message is:

Error 7 Unable to copy file "obj\Debug\AssemblyName.dll" to "bin\AssemblyName.dll". The requested operation cannot be performed on a file with a user-mapped section open.

I think this is because the previous file in bin-folder is not accessible. When I try to delete the file manually, I get an error "The action can't be completed because the file is open in another program". If I try to see what application locks the file with Unlocker, I don't get any results (No Locking handle found).

If I restart Visual Studio, the error goes away but happens again after a build or two. Goes without saying that this is seriously slowing me down. Any advice how to start solving this?

Answer 1

VIsual Studio 2012 on Windows 8. I was receiving the same error message on my project. Restarting Visual Studio or cleaning the obj folder manually did not help. Finally I closed all open files (Windows -> Close All Documents) and the problem went away.

Answer 2

This behavior was due to a newly installed Visual Studio extension called Visual Studio Achievements (http://visualstudiogallery.msdn.microsoft.com/bc7a433b-b594-48d4-bba2-a2f24774d02f)

I noticed that the .pdb file was locked by FxCop (using Unlocker) and I think that the Achievements -extension uses it. After disabling the extension I've no longer got the error mentioned above.