Unable to copy file reference.dll to bin/reference.dll. The process cannot access the file reference.dll because it is being used by another process

Question

For one of my ASP.NET 3.5 applications, every single time I try to build the web app, it throws the following build errors in Visual Studio 2008:

Error 16

Answer 1

you can also delete bin and obj folders in all projects in solution then rebuild solution.

Answer 2

File locks are just part of working with Visual Studio. There aren't any great ways to get around this problem.

Answer 3

I was using Visual Studio 2012 when this started happening on a 7 year old solution (for the second or third time: I've been to this question before).

I tried the various voodoo. I cleaned the solution. Didn't work. I restarted Visual Studio. Didn't work. I was confident that last one would work, because that is the voodoo that worked last time.

Ultimately, I remembered a security update had installed last night and was configured when I started my machine this morning - (Connected or not? No Idea) - So, I restarted Windows, and voila, it all worked like magic again.

Thanks MS for more mind mincing.

Answer 4

Similar to Benoit's answer but doesn't require any tool installation, you can use tasklist (task manager) command at the command line with the '/m' switch to get a list of processes using the dll:

tasklist /m mylocked.dll

I saw some posts indicating you have to do it from the directory of the offending dll, but I haven't found that to be the case.

Answer 5

This happens to me sometimes when using Visual Nunit for unit tests.

It seems the process 'VisualNunitRunner.exe' locks the .dll files in the destination directory.

I used Unlocker to find the process, kill it or unlock the files.

Answer 6

If you have Visual Nunit, it must be locking dll file.

1. Close VS
2. Go to taks manager , kill the Visual Nunit process
3. Now open VS and build the project