List<int> initializers = new List <int>();initializers.Add(1);initializers.Add(3);int index = initializers.IndexOf(3);initializers.Insert(index, 2);
Gives you 1,2,3.
Use List<T>.Insert:
List<T>.Insert
initializers.Insert(index, value);
You can just use List.Insert() instead of List.Add() to insert items at a specific position.