// use namespace here
    using System.Net.Mail;
    using System.Net;

    namespace SMTPConnection
    {
        public class Program
        {
            // Main Function
            static void Main()
            {
                string smtpServer = "smtp.gmail.com";
                int  smtpPort = 587;
                // Call SendEmail Function
                SendEmail(smtpServer, smtpPort);
            }            
            // Send Email Function
            private static void SendEmail(string smtpServer, int smtpPort)
            {
                SmtpClient smtpClient = new SmtpClient(smtpServer, smtpPort);
                smtpClient.EnableSsl = true;
                MailAddress mailAddressFrom = new MailAddress("demomailfrom@gmail.com");
                MailAddress mailAddressTo = new MailAddress("demomailto@gmail.com");
                MailMessage mailMessage = new MailMessage(mailAddressFrom, mailAddressTo);
                mailMessage.Body = "Body :- This is The Test Email";
                mailMessage.Subject = "Subject :- Test Email";
                NetworkCredential emailCredential = new NetworkCredential("demomailfrom@gmail.com", "demomailpassword");
                smtpClient.Credentials = emailCredential;                
                try
                {
                    smtpClient.Send(mailMessage);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Exception is:" + ex.ToString());
                }
                Console.WriteLine("Email Sent");
            }
        }
    }