C#

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

namespace Demo
    {
    class Program
        {
        static void Main(string[] args)
            {

...

            }
        }
    }

string name;
Console.Write("Enter your name: ");
name = Console.ReadLine();

Console.WriteLine("\nWelcome :" + name);
Console.WriteLine("1) Game Menu");
Console.WriteLine("2) List Users");
Console.WriteLine("3) Help");
Console.WriteLine("9) Quit");
Console.Write("Choice : (1,2,3 or 9) ");

            int i = 0;
            do
                {

...


                }
            while (i != '9');

string s = Console.ReadLine();
if (s == "")
    {
    continue;
    }

i = s[0];
switch (i)
    {
    case '1':
        Console.WriteLine("Game selected");
        // Handle game.
        break;
    case '2':
        Console.WriteLine("List selected");
        // List users
        break;
    case '3':
        Console.WriteLine("Help selected");
        // Help
        break;
    case '9':
        Console.WriteLine("Quit selected");
        break;
    default:
        Console.WriteLine("Invalid Key");
        break;
    }

string s = Console.ReadLine();
if (s == "")
    {
    continue;
    }
i = s[0];

ConsoleKeyInfo cki;
cki = Console.ReadKey(true);
i = (int) cki.Key;

1). Add a TextBox control to your form and also add a Button control.<br />
<br />
2). Now double-click the button control and the Button_Click event handler appears.<br />
<br />
3).Add the code given below to the Button_Click event handler:<br />
<br />
<pre>private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "YourCDkeyHere")
            {
                  //Steps to perform if the CDkey is correctly entered
            }
            else
            {
                  //Steps to perform if the CDkey is entered incorrectly
            }
        }
</pre><br />
<br />
<br />
So, here you are my dear fellow student. <br />
<br />
Wish you a very happy programming,<br />
Rajdeep.NET :-D