Different combinations of an array (C#)

Question

how can we find out different combination of the elements of an array using c# code. are there any inbuilt library function for this.?

for eg: suppose an array has e

Answer 1

Seemed logic is not absolutely correct as:

var cnk = comb(new[] { 1, 2, 3, 4 }, 3);

This gives 3 variants, but as a matter of fact it is 4:

1 2 3
1 2 4
1 3 4
2 3 4

I guess comb is better to be implemented in recursive way.