.Net Tips — Use LINQ to avoid nested loops

Admit it, we’ve all done it before, writing those nasty nested loops just so we can iterate through multiple lists to get some combination/permutation of the lists, e.g.:

1: for (int i = 0; i < 10; i++)
2: {
3:     for (int j = 0; j < 10; j++)
4:     {
5:         for (int k = 0; k < 10; k++)
6:         {
7:             // do something
8:         }
9:     }
10: }

This code obviously works and well understood amongst developers, but it’s not very readable and trying to terminate the outer loops from the inner loops is a pain and requires you to use one or more boolean flags which you need to track on every iteration at potentially every level of your loop…

A better way to solve this common problem is to use LINQ to ‘flatten’ the nested loops into a single loop:

1: var triplets = from I in Enumerable.Range(0, 10)
2:                from J in Enumerable.Range(0, 10)
3:                from K in Enumerable.Range(0, 10)
4:                select new { I, J, K };
5:
6: foreach (var triplet in triplets)
7: {
8:     // do something
9: }

Sweet, right? :-)