Yan Cui
I help clients go faster for less using serverless technologies.
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? :-)
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How do you use these I J and K variables?
@Anonymous – if you mean inside the foreach loop, you will be able to reference them like triplet.I, triplet.J and triplet.K.
In the LINQ query, you can reference the variables I, J and K directly, for example:
from I in Enumerable.Range(0, 10)
from J in Enumerable.Range(0, 10)
from K in Enumerable.Range(0, 10)
select new { Sum = I + J + K }