C#: How would you make a unique filename by adding a number?

Question

I would like to create a method which takes either a filename as a string or a FileInfo and adds an incremented number to the filename if the file

Answer 1

If checking if the file exists is too hard you can always just add a date and time to the file name to make it unique:

FileName.YYYYMMDD.HHMMSS

Maybe even add milliseconds if necessary.