Detailed explanation of the insertion of one-dimensional arrays in C#

using System;
using ;
using ;
using ;
using ;
using ;

namespace Array
{
  class Program
  {
    static void Main(string[] args)
    {
      int[] array = new int[] { 1, 2, 3 };
      int[] des = addArray(array, 4, 4); 
      foreach (int item in des)
      {
        (item );
      }
      ();
    }
    static int[] addArray(int[] bornArray, int index, int value)
    {
      ArrayList list = new ArrayList(bornArray );
      if (index <0)
      {
        index =0 ;
      }
      if (index >bornArray .Length -1)
      {
        index = ;
      }
      (index ,value );
      int[] des = new int[ ];
      for (int i=0;i<;i++)
      {
        des[i] = (int)list[i];
      }
      return des;
    }
  }
}