using System;

​

public delegate void ItemFoundCallback(int index);

​

public static class ItemFinder{

    public static void FindItem(string[] list, string stringToFind, ItemFoundCallback callback){

        for(int i = 0; i <list.Length; i++ ){

            if(list[i].Equals(stringToFind) == true){

                callback(i);

            }   

        }

    }

}

​

public class Program

{

    public static  void Announce(int i) {

        Console.WriteLine("String found at index {0}!", i);

    }

    public static void Main()

    {

        string[] s = {"Pikachu", "Squirtle", "Ditto", "Pikachu", "Ditto", "Dragonite"};

        Console.WriteLine("Finding Pikachu...");

        ItemFinder.FindItem(s, "Pikachu", Announce);

        Console.WriteLine("Finding Ditto...");

        ItemFinder.FindItem(s, "Ditto", Announce);

    }

}