log in to a site programatically using C# - asp.net

Question

I want to log in to a website setting.fun-freak.com just for learning purpose by using a windows desktop application. I used webrequest and tried as
string formUrl = "http://setting.fun-freak.com/Account/Login.aspx";
string formParams = string.Format("ctl00$MainContent$txtUserName=loginId&ctl00$MainContent$txtPassword=password");
string cookieHeader;
WebRequest req = WebRequest.Create(formUrl);
req.ContentType = "application/x-www-form-urlencoded";
req.Method = "POST";
byte[] bytes = Encoding.ASCII.GetBytes(formParams);
req.ContentLength = bytes.Length;
using (Stream os = req.GetRequestStream())
{
os.Write(bytes, 0, bytes.Length);
}
using (StreamReader sr = new StreamReader(req.GetResponse()))
{
pageSource = sr.ReadToEnd();
}
I assume that this pageSource object will have html of next page after login page (if login succesfully), but it contains the same login page in return.
How can I successfully log in to this website and get home page in response?
Moreover, this (setting.fun-freak.com) my own site, built in asp.net webforms. Here is button click event code (May be it help to dig out the problem)
UserContainer User = new UserProcessing().Authenticate(txtUserName.Text, txtPassword.Text);
if (User != null)
{
Session["User"] = User;
FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, RememberMe.Checked);
}
else
{
lblMessage.Text = "Invalid credentials. Please try again";
}
Any help will be appreciated.

Answer 1

I added this piece of code as it is, but it still not working .
it is taken from http://msdn.microsoft.com/en-us/library/debx8sh9.aspx
// Create a request using a URL that can receive a post.
WebRequest request = WebRequest.Create("http://setting.fun-freak.com/Account/Login.aspx");
// Set the Method property of the request to POST.
request.Method = "POST";
// Create POST data and convert it to a byte array.
string postData = "ctl00$MainContent$txtUserName=UserName&ctl00$MainContent$txtPassword=Password";
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Set the ContentType property of the WebRequest.
request.ContentType = "application/x-www-form-urlencoded";
// Set the ContentLength property of the WebRequest.
request.ContentLength = byteArray.Length;
// Get the request stream.
Stream dataStream = request.GetRequestStream();
// Write the data to the request stream.
dataStream.Write(byteArray, 0, byteArray.Length);
// Close the Stream object.
dataStream.Close();
// Get the response.
WebResponse response = request.GetResponse();
// Display the status.
Console.WriteLine(((HttpWebResponse)response).StatusDescription);
// Get the stream containing content returned by the server.
dataStream = response.GetResponseStream();
// Open the stream using a StreamReader for easy access.
StreamReader reader = new StreamReader(dataStream);
// Read the content.
string responseFromServer = reader.ReadToEnd();
// Display the content.
Console.WriteLine(responseFromServer);
// Clean up the streams.
reader.Close();
dataStream.Close();
response.Close();
The problem is that the object responseFromServer do not show then content of next to the login page. Its shows only login page contents.