Build error: “The process cannot access the file because it is being used by another process”

Question

I\'ve got a C# webforms app, that until today had been working just swimmingly.

Now today, all of a sudden, every time I try run the app, I get a file l

Answer 1

In my case there were some vstest processes running (with various names but all containing the string vstest). I had to terminate them in taskmgr.