Step 1:
Create a new project in Microsoft Visual Studio 2008 (File -> New -> Project -> Visual C# -> Console Application). Give SMS_Sender name and also specify the location where to store the project.

Step 2:
Now add a new item to the project we just created (Project -> Add New Item -> Class). Specify a name to the class as ‘TNV_SMSHelper’. The code now looks like as follows.
The namespace used is
using System.IO;
using System.Net;

public class TNV_SMSHelper
{
    private WebResponse myResponse = null;
    private string result = string.Empty;
    private string formatUrl(string ToMobileNo, string Message)
    {
        DateTime mydate = System.DateTime.Now;
        string url = "";
        url += "method=sendMessage";
        url += "&userid=2000053959"; // your loginId - 1
        url += "&password=Gdgek2yiY";//password - 2
        url += "&msg=" + mydate.ToString();
        url += Message;
        url += "&send_to="; // a valid 10 digit phone no.
        url += ToMobileNo;
        url += "&v=1.1";
        url += "&msg_type=TEXT"; // Can by "FLASH" or "UNICODE_TEXT" or "BINARY"
        url += "&auth_scheme=PLAIN";
        return url;
    }

    public string SendSms(string ToMobileNo , string Message)
    {
        try
          {
            string finalUrl = "http://enterprise.smsgupshup.com/GatewayAPI/rest?" + 
                                                  formatUrl(ToMobileNo, Message);
            HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(finalUrl);
            myResponse = myRequest.GetResponse();
            Stream st = myResponse.GetResponseStream();

            Encoding ec = System.Text.Encoding.GetEncoding("utf-8");
            StreamReader reader = new System.IO.StreamReader(st, ec);

            result = reader.ReadToEnd();

            reader.Close();
            st.Close();
            return result;
        }
        catch (Exception exp)
        {
           return result;
        }
        finally
        {
            if (myResponse != null) myResponse.Close();
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        TNV_SMSHelper smsObj = new TNV_SMSHelper();
       string Text = smsObj.SendSms("1234567890", "HelloWorld");
       Console.WriteLine(Text);
    }
}