Does .NET have built-in techniques for more complicated forms of iteration like the following:

1. Iterate over rearrangements of a list.
2. Iterate over subsets of a list.
3. Iterate over all indexes of a multidimensional list.
4. Iterate over all "combinations" of a list, i.e. all subsets of a list of a given length, where subsets that differs only in their ordering occur only once total.

I recently had cause to do (1) and my method was ugly, slow, tedious, and generalized poorly, which is why I ask. I can think of better ways, but it was garbage code anyway [brute force checking that there are precisely 576 seven-digit numbers made up of 1, 2, 3, 4, 5, 6, and 7 that are also divisible by 11]. The others are just for my own curiosity.