I want to log in to a website using C# code..

The main aim is to check whether the username and password I provide is
correct or not.

I used the following code

bool somefunction()
{
string username = textbox1.text;
string password = textbox2.text;

string url = "http://youtube.com/signup?username=" + textBox2.Text +
"&password=" + textBox3.Text + "&current_form=loginForm&action_login=1";

HttpWebRequest req = (HttpWebRequest)WebRequest.Create(str);
req.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)";
req.ContentType = "application/x-www-form-urlencoded";
req.Method = "POST";

HttpWebResponse resp = (HttpWebResponse)req.GetResponse();

CookieCollection cookie;

           cookie = resp.Cookies;

           bool success = false;

           foreach (Cookie c in cookie)
           {
               if (c.Name == "LOGIN_INFO" && c.Value != "")
               {
                   success = true;
               }
           }

return success;
}

But however it shows an exception........

System.Net.WebException was unhandled
 Message="The server committed a protocol violation.
Section=ResponseStatusLine"
 Source="System"
 StackTrace:
      at System.Net.HttpWebRequest.GetResponse()
      at ContentExtractor.form3.button1_Click(Object sender, EventArgs e)
in G:\Docs\Kitty\Visual Studio
2005\Projects\Earnings\ContentExtractor\ContentExtractor\form3.cs:line 38
      at System.Windows.Forms.Control.OnClick(EventArgs e)
      at System.Windows.Forms.Button.OnClick(EventArgs e)
      at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
      at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons
button, Int32 clicks)
      at System.Windows.Forms.Control.WndProc(Message& m)
      at System.Windows.Forms.ButtonBase.WndProc(Message& m)
      at System.Windows.Forms.Button.WndProc(Message& m)
      at
System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
      at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&
m)
      at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd,
Int32 msg, IntPtr wparam, IntPtr lparam)
      at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&
msg)
      at
System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32
dwComponentID, Int32 reason, Int32 pvLoopData)
      at
System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32
reason, ApplicationContext context)
      at
System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason,
ApplicationContext context)
      at System.Windows.Forms.Application.Run(Form mainForm)
      at ContentExtractor.Program.Main() in G:\Docs\Kitty\Visual Studio
2005\Projects\Earnings\ContentExtractor\ContentExtractor\Program.cs:line 17
      at System.AppDomain._nExecuteAssembly(Assembly assembly, String[]
args)
      at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence
assemblySecurity, String[] args)
      at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
      at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
      at System.Threading.ExecutionContext.Run(ExecutionContext
executionContext, ContextCallback callback, Object state)
      at System.Threading.ThreadHelper.ThreadStart()

The original login form is located at http://www.youtube.com/index

and however if I happen to type the url

string url = "http://youtube.com/signup?username=" + textBox2.Text +
"&password=" + textBox3.Text + "&current_form=loginForm&action_login=1";

Can anyone help me how to do this..

And I also need an overview of how to post into any website form if I know
the field names and the action url is known...

Thanks in advance

Regards
Rajkiran