What is the code for sending email in asp.net

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.Mail;
using System.Net.Mime;

namespace Gmail
{
    public partial class Form1 : Form
    {
        //String path;
        MailMessage mail = new MailMessage();
        public Form1()
        {
            InitializeComponent();
        }

        private void Button1_Click(object sender, EventArgs e)
        {
            SmtpClient SmtpServer = new SmtpClient();
            SmtpServer.Credentials = new System.Net.NetworkCredential("your e-mail id", "password");
            SmtpServer.Port = 587;
            SmtpServer.Host = "smtp.gmail.com";
            SmtpServer.EnableSsl = true;
            mail = new MailMessage();
            String[] addr = TextBox1.Text.Split(',');
            try 
            {
                mail.From = new MailAddress("your email id", "Developers", System.Text.Encoding.UTF8);
                Byte i;
                for( i = 0;i< addr.Length; i++)
                    mail.To.Add(addr[i]);
                mail.Subject = TextBox3.Text;
                mail.Body = TextBox4.Text;
                if(ListBox1.Items.Count != 0)
                {
                    for(i = 0;i<listbox1.items.count;i++)>
                    mail.Attachments.Add(new Attachment(ListBox1.Items[i].ToString()));
                }
                mail.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
                mail.ReplyTo = new MailAddress(TextBox1.Text);
                SmtpServer.Send(mail);
                MessageBox.Show("Mail Send");
            }
            catch (Exception ex){
            MessageBox.Show(ex.ToString());
            }
        }
}
}

public Boolean SendingMail(string From, string To, string Subject,string Body)
	{
        try
        {
            MailMessage m = new MailMessage("mailidofSender", To);
            m.Subject = Subject;
            m.Body = Body;
            m.IsBodyHtml = true;
            SmtpClient smtp = new SmtpClient();
            smtp.Host = "mail.google.com";
            NetworkCredential authinfo = new NetworkCredential("mailidfrom", "YourPassword");
            smtp.UseDefaultCredentials = false;
            smtp.Credentials = authinfo;
            smtp.Send(m);
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
	}

string subject = "mention subject here";
        try
        {
            
            string emailTo = "uremail";
            string emailfrom="uremail";
            string body = "urbody";
            MailMessage objmail = new MailMessage(emailfrom, emailTo, subject,body);


            SmtpClient smtpclnt = new SmtpClient("smtp.gmail.com", 587);
            smtpclnt.DeliveryMethod = SmtpDeliveryMethod.Network;

            smtpclnt.UseDefaultCredentials = true;
            smtpclnt.EnableSsl = true;
            smtpclnt.Credentials = new System.Net.NetworkCredential("username", "password");
            smtpclnt.Send(objmail);
        }
        catch (Exception ex)
        {
           
        }