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.

Use

Path.GetTempFileName()

or use new GUID().

Path.GetTempFilename() on MSDN.

System.IO.Path.GetRandomFileName()

Path.GetRandomFileName() on MSDN.