using System;

​

public class Program

{

    public static void Main()

    {

        int val1 = 10;

        int val2 = 15;

        Console.WriteLine($"Before swap: value 1 = {val1}, value 2 = {val2}");

        static void swap(ref int num1, ref int num2)

        {

            int s = num1;

            num1 = num2;

            num2 = s;

        }

        swap(ref val1, ref val2);

        Console.WriteLine($"After swap: value 1 = {val1}, value 2 = {val2}");

​

​

    }

}