how do i use serial key for my application

        using Microsoft.Win32;
        private void Form1_Load(object sender, EventArgs e)
        {
            RegistryKey regkey = Registry.CurrentUser.OpenSubKey(@"Softwares\CompanyName\", true);
            string Serial = regkey.GetValue("AppSerial","").ToString();

            regkey.Close();
            if (Serial != "YourCustome generated Serial")
            {
                // Show Serial Validation Dialog 
                
                SerialDialog sd = new SerialDialog();
                SerialDialog.ShowDialog();

                //Now Write Code For Form Closing if User Gives Wrong Serial number !!
            }
        }