collections.md

Collections

Perform Side Effects Using Apply and Do

Instead of using a foreach loop, you can use Apply or Do to execute some Action<T> or Action<T, int> for each item in the collection.

The Apply extension method returns no value.

new { 1, 2, 3 }.Apply(i => Console.WriteLine(i));

// 1
// 2
// 3

new { "ITEM1", "ITEM2", "ITEM3" }.Apply((item, index) => Console.WriteLine($"[{index}] = {item}"));

// [0] = ITEM1
// [1] = ITEM2
// [2] = ITEM3

The Do extension method returns the original collection. This method is useful when you want to perform additional processing on the collection after applying side effects.

// returns { 1, 2, 3 }
new { 1, 2, 3 }.Do(i => Console.WriteLine(i));

// 1
// 2
// 3

// returns { "ITEM1", "ITEM2", "ITEM3" }
new { "ITEM1", "ITEM2", "ITEM3" }.Do((item, index) => Console.WriteLine($"[{index}] = {item}"));

// [0] = ITEM1
// [1] = ITEM2
// [2] = ITEM3