Unable to send an email

 It didn't prompt out any error, but still i cant received the email that i send, can anyone help me?Thanks
Here is my code:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Net;
using System.Net.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;
using System.IO;
using System.Drawing;

public partial class _Register : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        
    }
    protected void btnRegister_Click(object sender, EventArgs e)
    {
        string name = txtName.Text;
   & ...