indexOf

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                string str1, str2;

                Console.WriteLine("Type the containing string");

               str1 = Console.ReadLine().ToLower();

               Console.WriteLine("Type A string to be found in the earlier string");

               str2 = Console.ReadLine().ToLower();

               Console.WriteLine("Result is "+ str1.IndexOf(str2).ToString() );

               Console.WriteLine("");
               Console.WriteLine("Any key to loop, exit to exit");
               if (Console.ReadLine().ToLower() == "exit") break;
               Console.WriteLine("");
            }
        }
    }
}