c# - Can using Ticks of DateTime.Now can generate duplicates unique identifiers?

Question

Is there a possibility for this code to generate the same identity,

for (int i = 0; i < 20; i++)
    {
        string TransID = DateTime.Now.Ticks.ToString();
    }

What are the considerations that make this happen?

Answer 1

Yes, this code can generate the same identifier.

Regardless of the tick precision, it can do so if the system date is changed in Windows and/or the Bios.

And also if it is run by computers in different time zones or if you travel.

The latter case implies that you should absolutely not use such a code even in local and not-connected applications.

If you need ID for a personnal and local application, and you never travel, this code does what you want, but it is not recommended to use such bad pattern.

As everyone says, without being wrong, you should use Guid.New() which is actually the safest standard, or an int or a long auto-increment (for local or managed by a server) for a better performance in some cases.

https://docs.microsoft.com/dotnet/api/system.datetime.now

https://en.wikipedia.org/wiki/Unique_identifier

https://en.wikipedia.org/wiki/Universally_unique_identifier

How expensive is a GUID cast and comparison vs a string comparison