How to generate UUID version 4 using c#

Question

My requirement is to generate version 4 UUID from C# code for google API session token and i am not sure Guid.NewGuid() method, Which version of GUID does it return. Like version

Read google and blog but not get sure answer Does Guid.NewGuid() produce UUID version 4 according to RFC4122?

Thanks in advance

Answer 1

GUIDs are V4... every single GUID you generate will look like this

18acac20-991e-437e-9529-a441452f6b7e
d6d68639-64c2-452e-95b7-16cf6dbf5301
b0943b6d-4779-4771-92bf-cc2d634fb671
218b5620-d30d-46d9-9c88-38a4ac64266e
de03042c-792f-4689-80ca-26287ceb2129
1175bb5d-d35e-4a46-aaac-0825c749dc3a
42864583-c0f6-4e44-8710-39c9a9146d43
223ca924-4b77-4931-bb94-c1d371894683
2c4495ab-19e4-4aeb-b647-10db8625791c
f5894345-cbe3-4fc7-92c3-d6d863f70411
              ^    ^
              1    2

The digit at position 1 above is always 4 and the digit at position 2 is always one of 8, 9, A or B.

You can confirm this by

var cts = new CancellationTokenSource();

var parallelOptions = new ParallelOptions() { MaxDegreeOfParallelism = 8, CancellationToken = cts.Token };
Parallel.For(0, int.MaxValue, parallelOptions, (i) =>
{
    var guid = Guid.NewGuid().ToString();
    var four = guid.ElementAt(14);
    var ab89 = guid.ElementAt(19);

    if (four != '4') cts.Cancel();
    if (ab89 != 'a' && ab89 != 'b' && ab89 != '8' && ab89 != '9') cts.Cancel();

    if ((i % 100000) == 0 && i < (int.MaxValue / 8))
    {
        Console.WriteLine($"{i * 8:n}"); // roughly   
    }
});

That will run through 4billion'ish attempts in a reasonable amount of time if you have doubts