Custom file extenstion in Visual Studio C#

I was using some files that have among other things some C# code in it in VS. When it dawned at me that I wasn’t getting the syntax highlighting which makes it much harder to read the code. Visual Studio just treats it as any other text file. In order to add a new one you just need to set new file association within VS. Tools - Options - Text editor - File Extensions. Add your extension and the editor you want to use, in my case Microsoft Visual C#. That will give you the code syntax, much better.