c# send mail inquiry

here is my code, it works, but i have a few questions.

    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Page_Init(object sender, EventArgs e)
        {
            btnSend.Click += new EventHandler(btnSend_Click);
        }

        void btnSend_Click(object sender, EventArgs e)
        {
            try
            {
  ...