using System;

using System.Collections; 

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        string enter;

        string myAdd;

        ArrayList myList = new ArrayList();

        Console.WriteLine("Enter 1-5 for operation");

        Console.WriteLine("[1] ADD");

        Console.WriteLine("[2] UPDATE");

        Console.WriteLine("[3] DELETE");

        Console.WriteLine("[4] SEARCH");

        Console.WriteLine("[5] DISPLAY ALL");

        Console.WriteLine("This is the list of items inside the array");

        foreach(string i in myList) 

        { 

            Console.WriteLine(i); 

        } 

        while (true) {

        Console.WriteLine("Enter Operation");

        enter = Console.ReadLine();

            //add

        if (enter == "1"){

            Console.WriteLine("Enter item you want to add");

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

            if (myList.Contains(myAdd.ToLower())){

                Console.WriteLine("Item already exists in array");

            }

            else{

                myList.Add(myAdd);          

                Console.WriteLine("Item Successfully added" );

                }

            }

    //update open       

        if (enter == "2"){

            Console.WriteLine("Enter index you want to update");

            int myIndex = Convert.ToInt32(Console.ReadLine());

            myList.RemoveAt(myIndex);

            Console.WriteLine("Enter the item that will replace");

            string myReplace = Console.ReadLine().ToLower();

            if (myList.Contains(myReplace.ToLower()))

                Console.WriteLine("Item already exists in array");

            else{

                myList.Insert(myIndex, myReplace);          

                Console.WriteLine("Item Successfully added" );

                }

            } //update close

    //delete

            if (enter == "3"){

            Console.WriteLine("Enter item you want to delete");

            String myDelete = Console.ReadLine().ToLower();

            if (myList.Contains(myDelete)){

                myList.Remove(myDelete);

                Console.WriteLine("Delete Successful");

            }

                else {

                    Console.WriteLine("Item does not exist in array");

                }

        } //delete close

            // search

        if (enter == "4"){

            Console.WriteLine("Enter item you want to search");

            String mySearch = Console.ReadLine().ToLower();

            if (myList.Contains(mySearch)){

                Console.WriteLine(mySearch + " is present at array");

                Console.WriteLine(myList.IndexOf(mySearch));

        }

            else {

                Console.WriteLine("Not present in array");

            }

        } // search close

            //display

        if (enter == "5") {

            foreach (string i in myList){

                Console.WriteLine(i);

                }

            }

        }

    }

}

​