using System;

using System.Collections.Generic;

​

public class Program

{

     public static void Main()

     {

          IEnumerable<IEnumerable<int>> collection = new List<List<int>>()

          {

              { 1, 2 },

              { 3, 4 },

          };

​

          collection.Dump();

     }

}

​

public static class ListExtensions

{

     public static void Add<T>(this List<List<T>> list, params T[] items)

     {

         list.Add(new List<T>(items));

     }

}