"Collection Initializers"

var myArray = new[] { 1, 2, 3, 4, 5 }; // myArray is an int[] of length 5
var myList = new List<int> { 1, 2, 3, 4, 5 }; // myList is a List<int> with 5 elements
var myDict = new Dictionary<int, int> { { 1, 100 }, { 2, 200 } }; // myDict is a Dictionary with 2 key-value pairs