Build error Unable to copy file. The process cannot access the file because it is being used by another process

Hi,

when having a Add-In  under development in VS run and applying changes to it and trying to rebuild the solution, I get the following error:

Unable to copy file "obj\Debug\MyAddIn.dll" to "bin\MyAddIn.dll". The process cannot access the file 'bin\MyAddIn.dll' because it is being used by another process.

The only solution is to close and restart Visual Studio.

Is there a way to unload a Add-In via the Add-In Manager without having to restart VS?
Do I have to unload something in my code?

Alex