VS 2019 All possible combinations in an integer array

Hi, i need to find a way of finding all possible combinations of an array full of numbers.
Have had a look but can't really find a true way of finding this anywhere, and i need it to not have repetition.

You guys did help out before but it did not really work as it had an element of randomisation to it.

Any help would be very much appreciated as i am not too hot with programming in general so please forgive this in advanced :-)

Cheers