c# - Divide a large IEnumerable into smaller IEnumerable of a fix amount of item

Question

In order to support an API that only accepts a specific amount of items (5 items), I want to transform a LINQ result into smaller groups of items that always contain that set amount of items.

Supposing the list {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18}

I want to get three smaller lists of a maximum of 5 items each

{1, 2, 3, 4, 5}

{6, 7, 8, 9, 10}

{11, 12, 13, 14, 15}

{16, 17, 18}

How can I do that with LINQ? I'm assuming that it either involves Group or Aggregate, but I'm having trouble figuring how to write that.

Answer 1

Try something like this:

var result = items.Select((value, index) => new { Index = index, Value = value})
                  .GroupBy(x => x.Index / 5)
                  .Select(g => g.Select(x => x.Value).ToList())
                  .ToList();

It works by partitioning the items into groups based on their index in the original list.