login into a WEB page programatically.

I'm logging into a WEB page programatically. Using HttpWebRequest, I am doing the following:

1) download the login WEB page.
2) Parse out the VIEWSTATE.
3) Create and encode post data.
4) POST it by writing to stream.

Here's my post data code:

 postData = String.Format(
                     "__VIEWSTATE={0}&Login1_UserName={1}&Login1_Password={2}&Login1_LoginButton=LOGIN",
                     viewState, username, password)

Now, I read an article about how to send the username and password. Login1_UserName and Login1_Password are the asp IDs of the textboxes for username and password, and Login1_LoginButton is the submit button.   Now upon post, I am getting back a page where there is a read asterisk next to the textboxes for username and password.  So, I must have submitted it correctly, but without the username and password.

Can anyone help me out? How do I send the username and password?