I want to ingore any file/folder that has:
_ReSharper
in the file or folder in my .gitignore file, is this possible?
I tried:
ReSharper
but that doesn't work.
I read your question as asking whether you can ignore all files and directories that contain _ReSharper as a substring of their name, in which case you can add the following line to your .gitignore:
*_ReSharper*
gitignore says "Files already tracked by git are not affected; see the NOTES below for details."