code for the login control

See this article, I am sure will help.

http://www.c-sharpcorner.com/UploadFile/raj1979/LoginControl07242008104351AM/LoginControl.aspx?ArticleID=e06b9d4f-b65c-4c63-babc-fb65ef3224f7

Try the following code:

using system.data.sqlclient;

using system.web.configuration;

Sqlconnection con = new sqlconnection("your conectionstring");

      or

Sqlconnection con = new Sqlconnection(WebconfigurationManager.connectionstrings["your connetion name"].connectionstring);

Sqlcommand cmd = new sqlcommand();

cmd.commandtext = "select * from table";

cmd.connection = con;

if (con.state==connectionstate.closed) con.open();

SqlDatareader dr = cmd.executereader();

while(dr.read)

{

       if ( dr["Username"] == textbox1.text.trim() && dr["Password"] == textbox2.text )

       {

                 response.redirect("Homepage.aspx");

               return;

        }

}

 

Please go through with following URL for your reference.
1.http://www.daniweb.com/forums/thread6028.html
2.http://www.daniweb.com/forums/thread6028.html