using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.Data;
using System.Data.SqlClient;
using System.Collections.Specialized;
using System.Text;

public partial class OTP : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Panel2.Visible = false;
    }

    protected void Button1_Click(object sender, EventArgs e)
    {

        Panel1.Visible = false;
        Panel2.Visible = true;
        Random random = new Random();
        int value = random.Next(1001, 9999);
        string destinaddr = "65" + txtMobileNo.Text;
        string message = "Your OTP Number is " + value + " ( Sent By : Unknown )";
        sendSMS(destinaddr, value.ToString());
    }

    public string sendSMS(string usernumber, string OTPCode)
    {
        String message = HttpUtility.UrlEncode("This is your OTP : " + OTPCode + ". This will expire in 30 seconds.");
        using (var wb = new WebClient())
        {
            byte[] response = wb.UploadValues("https://api.txtlocal.com/send/", new NameValueCollection()
                {
                {"apikey" , "iM91uB/r99c-76KWeOLoMqbH2hRCwqgkdUsGeK0fo2"},
                {"numbers" , usernumber},
                {"message" , message},
                {"sender" , "OTP"}
                });
            string result = Encoding.UTF8.GetString(response);
            return result;
        }
    }

protected void Button2_Click(object sender, EventArgs e)
    {
        string OTP = txtOTP.Text;
        if(OTP == txtOTP.Text)
        {
            Label1.Text = "Verified";
        }
        else
        {
            Label1.Text = "Incorrect OTP";
        }
    }
}