How to login Secured https website using asp.net c# programatically

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C#

C#4.0

ASP.NET4

Hello,
can anyone help me out, in login to a website(programatically) that is https. I have the username and password of that site. I am using HttpWebRequest and HttpWebResponse..

my code is as follow:-

CookieContainer cookies = new CookieContainer();
WebRequest loginRequest;
//Go to login page so that we get a cookie
loginRequest = (HttpWebRequest)HttpWebRequest.Create("https://sitename");
loginRequest.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(ASCIIEncoding.ASCII.GetBytes("" + TextBox1.Text + ":" + TextBox2.Text + "")));
loginRequest.UseDefaultCredentials = true;
loginRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)";
loginRequest.CookieContainer = cookies;
loginRequest.AllowAutoRedirect = false;

HttpWebResponse loginResponse = (HttpWebResponse)loginRequest.GetResponse();

//Now that we have the cookie we can do a proper login
HttpWebRequest doLogin = (HttpWebRequest)HttpWebRequest.Create("https://siteName");

//doLogin.UseDefaultCredentials = true;
doLogin.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)";
doLogin.Method = "POST";
doLogin.ContentType = "text/html;charset=UTF-8";
doLogin.AllowAutoRedirect = false;

using (StreamWriter sw = new StreamWriter(doLogin.GetRequestStream()))
{
sw.Write("usr=<username>&pass=" +TextBox2.Text + "&mc=1&guid=&dbnum=0&ic=1&task=dologin&app=library&x=32&y=10");

}

doLogin.CookieContainer = cookies;
doLogin.Referer = "https://secure.sbigeneral.in/Extranet/faces/premiumcalc_landingpage";

HttpWebResponse Response = (HttpWebResponse)doLogin.GetResponse();

string resphead = Response.Headers["Set-Cookie"];

string resp = Response.StatusCode.ToString();

using (StreamReader sr = new StreamReader(Response.GetResponseStream()))
{
string textresponse = sr.ReadToEnd();

}