foreach.cs

using System;
using System.Collections.Generic;

class Program {
  static void Main(string[] args) {
    List<List<int>> arr = new List<List<int>>();

    // -> []

    for(int i = 0; i < 10; ++i) {
      arr.Add(new List<int>());
    }

    // -> [[], [], [], [], [] ... etc]

    for(int i = 0; i < 10; ++i) {
      for(int j = 0; j < 10; ++j)
        arr[i].Add(j);
    }

    // I
    foreach(List<int> i in arr) {
      foreach(int j in i)
        Console.Write(j + " ");
      Console.WriteLine();
    }

    // II
    for(int i = 0; i < arr.Count; ++i) {
      for(int j = 0; j < arr[0].Count; ++j)
        Console.Write(j + " ");
      Console.WriteLine();
    }
  }
}