Sending image Through mail

Im trying to send a image attachement through mail ,it is not working please give me suggesutions in code,with out attachement code works fine,by addding attachements it dint works
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.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;
 
public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Write(sentmail("tu ...