nCr in C#

combination.cs

using System;
class combi
{
  static int[] arr;
  public static void Main()
  {
    arr  = new int[] {1,2,3,4,5};
    Cal(3,0,new int[3]);
  }
  static void Cal(int len,int start,int[] result)
  {
    if(len == 0)
    {
      Print(result);
      return;
    }
    for(int i = start ; i<=arr.Length-len ; i++)
    {
      result[result.Length-len] = arr[i];
      Cal(len-1,i+1,result);
    }
  }
  static void Print(int[] arr)
  {
    int len = arr.Length;
    for(int i=0 ; i<len ; i++)
    {
      Console.Write(arr[i] + " ");
    }
    Console.WriteLine();
  }
}

thank you so much yehyeh