Variations without Repetition in C#

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C#

I have a set of numbers
Is not known how many number inside

For Example:

in the list [1,2,3,4]

i want out put the result:

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

I want to answer in this article and another article is not in the sense explained in detail here in this article.