Need a .NET Framework 4 C# Code Snippet which can send emails with Authentication

SmtpClient objSmtpClient = new SmtpClient("smtp.sendgrid.net", 587);
objSmtpClient.UseDefaultCredentials = false;
objSmtpClient.Credentials = new System.Net.NetworkCredential("apikey", "SG.GRhs8LSzR4KNhbyQavpSPw.2Pfbd0jWVj9mZj2IirBG1xHPJ6bbyC7nz8SVX");
objSmtpClient.EnableSsl = false;
objSmtpClient.Timeout = 30000;
objSmtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
objSmtpClient.Send(objMailMessage);

The following code doesn't work. Need a working script. API Key is wrong so don't try that. Need to use your own.