The answer to this is not as straightforward as the question. Firstly, do you have an SMS provider already, or are you planning on hosting an SMS gateway yourself?
If the answer is no to both the above then you need to first determine how you are going to send the SMS once a process has created one.
You need a provider - or a way of actually passing the SMS onto a gateway. You can't really do anything else until you know how you will get the SMS into the airwaves!
Once you have a provider they will usually have an API or a web service you can use to call their sending methods. Once you have this you can code a solution to sending the SMS, then the web part to pass the information to the service.
i found this sms provider ipip.com
they supported me with this code
private void button1_Click(object sender, EventArgs e)
string toPhoneNumber = toTextBox.Text;
string login = fromTextBox.Text;
string password = passTextBox.Text;
string compression = subjectTextBox.Text;
string body = bodyTextBox.Text;
MailMessage mail = new MailMessage();
mail.To = toPhoneNumber + "@sms.ipipi.com";
mail.From = login + "@ipipi.com";
mail.Subject = compression;
mail.Body = body;
System.Web.Mail.SmtpMail.SmtpServer = "ipipi.com";
/*set the addresses
mail.From = new MailAddress("firstname.lastname@example.org");
//set the content
mail.Subject = "This is an email";
mail.Body = "this is a sample body";
//send the message
SmtpClient smtp = new SmtpClient("127.0.0.1");
but it didnt work