Why can I initialize a List like an array in C#?

Question

Today I was surprised to find that in C# I can do:

List a = new List { 1, 2, 3 };

Why can I do this? What constructor

Answer 1

It is so called syntactic sugar.

List is the "simple" class, but compiler gives a special treatment to it in order to make your life easier.

This one is so called collection initializer. You need to implement IEnumerable and Add method.