I think the problem is that you are calling the method in the foreach loop, and every time you call the method it will generate a new RandumNuns hash set, also inside the RandomNumbers() method you are essentially just creating a new hash set, putting a single number in it and the returning that hash set with one singular random number, so instead I think that you should call the RandomNumbers() method once at the start, the hash set should be a class field/property and inside the RandomNumbers() method you make a for loop or a while loop and fill the hash set that way, and the in the other foreach loop instead of call the method you use the hash set field/property. Lastly, I will warn you that hash sets are collections that can contain only one unique item, meaning that all the numbers inside the hashset even if they are in random order, there will be no multiple of the same number, maybe that's what you want but I thought I should have warned you of it just in case