Constantly Incrementing String
===

So, what I'm trying to do this something like this: (example)

a,b,c,d.. etc. aa,ab,ac.. etc. ba,bb,bc, etc.


So, this can essentially be explained as generally increasing and just printing all possible variations, starting at a. So far, I've been able to do it with one letter, starting out like this: 

    for (int i = 97; i <= 122; i++)
    {
        item = (char)i
    }

But, I'm unable to eventually add the second letter, third letter, and so forth. Is anyone able to provide input? Thanks.