DevStudent

ref stands for reference and out stands for output.

ref parameter variable should be initialized before we call the method. That value will be used a as reference value in the method.

out parameter variable initialization is not required but it should be returned by the method.

Example program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FirstConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Program p = new Program();
            //val1 has to be initialized
            int val1 = 10;
            p.Add(ref val1);
            //val2 initialization not required
            int val2;
            int j = p.Sub(out val2);
            Console.WriteLine(j);
            Console.ReadKey();

        }

        public void Add(ref int val1)
        {            //code goes here
            Console.WriteLine("Hello");
        }
        public int Sub(out int val2)
        {
//val2 is changed from 2 to 5
            val2 = 5;
            return val2;
        }
    }
}