Start of the Cannot Create/Shadow Copy 'xxxx" when that file already exists.
Solution #2 of Cannot Create/Shadow copy 'xxx' when that file already exists -- web config solution
Solution #3 - w3p or aspnet to cannot create shadow copy when that file exists
Try this as your first solution:
If you just made a change to a file in the App_Code directory, or just imported some files into the App_Code directory or the Bin directory, wait for Visual Studio to finish compiling and stabilizing.
This message comes up often if you have been debugging or working with some code and then make a quick change in an App_Code directory file. If this doesn't work, go to the "web config solution.
Alternate Solutions to Consider