can not add View error: Avoid use of “\\.\” in the path

I get a strange error when Adding new view suddenly after I write this code for encrypt-and-decrypt-URL in this link https://dotnettrace.net/2013/09/19/encrypt-and-decrypt-url-in-mvc-4/

get this error message:

"FileStream will not open Win32 devices such as disk partitions and tape drives. Avoid use of "\.\" in the path."

I can't understand why this error occurs. I have never got this error before.

What can be the problem?

Note: I am using Visual Studio 2017