How To get String Substring in C Sharp

using System;

class Samplestring
{
  public static void Main()
{
    string string = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    Console.WriteLine("string: " + string);
   
    Console.Write("string.Substring(16): ");
    string substr = string.Substring(16);
    Console.WriteLine(substr);

  }
}
------------------
string: ABCDEFGHIJKLMNOPQRSTUVWXYZ
string.Substring(16): QRSTUVWXYZ
---------------------------------------------

C# Program how to Swap two Numbers

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Program
{
    class SwapProgram
    {
        static void Main(string[] args)
        {
            int number1, number2, temp;
            Console.Write("\nEnter the First Number : ");
            number1 = int.Parse(Console.ReadLine());
            Console.Write("\nEnter the Second Number : ");
            number2 = int.Parse(Console.ReadLine());
            temp = number1;
            number1 = number2;
            number2 = temp;
            Console.Write("\nAfter Swapping : ");
            Console.Write("\nFirst Number : " + number1);
            Console.Write("\nSecond Number : " + number2);
            Console.Read();
        }
    }
}
---------------
OUTPUT:

Enter the First Number : 50
Enter the Second Number : 100

After Swapping :

First Number : 100
Second Number : 50
---------------------------------------------