How to Generate unique file names in C#

Question

I have implemented an algorithm that will generate unique names for files that will save on hard drive. I'm appending DateTime: Hours,Minutes,Second and Milliseconds but still it generates duplicate name of files because im uploading multiple files at a time.

What is the best solution to generate unique names for files to be stored on hard drive so no 2 files are same?

Answer 1

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.

Answer 2

Use

Path.GetTempFileName()

or use new GUID().

Path.GetTempFilename() on MSDN.