How to Generate unique file names in C#

If readability doesn’t matter, use GUIDs.

E.g.:

var myUniqueFileName = string.Format(@"{0}.txt", Guid.NewGuid());

or shorter:

var myUniqueFileName = $@"{Guid.NewGuid()}.txt";

In my programs, I sometimes try e.g. 10 times to generate a readable name (“Image1.png”…”Image10.png”) and if that fails (because the file already exists), I fall back to GUIDs.

Update:

Recently, I’ve also use DateTime.Now.Ticks instead of GUIDs:

var myUniqueFileName = string.Format(@"{0}.txt", DateTime.Now.Ticks);

or

var myUniqueFileName = $@"{DateTime.Now.Ticks}.txt";

The benefit to me is that this generates a shorter and “nicer looking” filename, compared to GUIDs.

Please note that in some cases (e.g. when generating a lot of random names in a very short time), this might make non-unique values.

Stick to GUIDs if you want to make really sure that the file names are unique, even when transfering them to other computers.