C#邮件发送的系统部分代码

using System.Net;
using System.Net.Mime;
using System.Net.Mail;
///////////////////////////////

protected void Button2_Click(object sender, EventArgs e)
{

MailAddress from = new MailAddress(tb_From.Text);
MailAddress to = new MailAddress(tb_To.Text);
MailMessage mailObj = new MailMessage(from, to);
mailObj.Subject = tb_Sub.Text;
mailObj.Body = tb_Body.Text;
// html格式的邮件
mailObj.IsBodyHtml = true;
// 设置为高级优先权
mailObj.Priority = MailPriority.High;

if (File1.Value.ToString()!="")
{
// 为邮件添加附件
Attachment addFile = new Attachment(File1.Value.ToString(), MediaTypeNames.Application.Octet);
mailObj.Attachments.Add(addFile);
}

SmtpClient sc = new SmtpClient();
sc.Host = "smtp.yeah.net";
sc.Credentials = new NetworkCredential("用户名", "密码");
sc.Send(mailObj);

Lab.Text = "发送完毕!";

}