Sending SMS from ASP.NET

Write a method in class file

public static void CreateRequestTOSENDSMS()
        {
            string url = "SMS gateway url, which will be provided by SMS people";//      HttpContext.Current.Request.Url.AbsoluteUri.ToString().Replace("AutoLogin", "Login");
            CookieContainer myCookieContainer = new CookieContainer();
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            request.CookieContainer = myCookieContainer;
            request.Method = "GET";
            request.KeepAlive = false;
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            System.IO.Stream responseStream = response.GetResponseStream();
            System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
            string srcString = reader.ReadToEnd();
             // Concat the string data which will be submit
            string formatString ="username={0}&pass={1}&senderid={2}&mtype=txt&tempid={3}&f1={4}&f2={5}&f3={6}&dest_mobileno={7}&response=Y";
            string postString = string.Format(formatString, "demo12", "demo123", "DEMOVL", "1018", "1234", "5673", "tyyty");
            byte[] postData = Encoding.ASCII.GetBytes(postString);

            // Set the request parameters
            request = WebRequest.Create(url) as HttpWebRequest;
            request.Method = "POST";
            request.Referer = url;
            request.KeepAlive = false;
            request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; CIBA)";
            request.ContentType = "application/x-www-form-urlencoded";
            request.CookieContainer = myCookieContainer;
            System.Net.Cookie ck = new System.Net.Cookie("SMS", "Value of SMS cookie");
            ck.Domain = request.RequestUri.Host;
            request.CookieContainer.Add(ck);
            request.CookieContainer.Add(response.Cookies);
            // Submit the request data
            System.IO.Stream outputStream = request.GetRequestStream();
            request.AllowAutoRedirect = true;
            outputStream.Write(postData, 0, postData.Length);
            outputStream.Close();
            // Get the return data
            response = request.GetResponse() as HttpWebResponse;
            responseStream = response.GetResponseStream();
            reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
            srcString = reader.ReadToEnd();
            }

The parameters "url", "formatstring" may vary from one SMS provider to another. Add these namespaces.
using System.Text;
using System.IO;
using System.Net;