write this cod on submit button : ..........

 HttpCookie objCookie = new HttpCookie("UserCookie");
            objCookie.Values.Add("UserName", TextBox1.Text);
            objCookie.Values.Add("UserPass", TextBox2.Text);
         
//for permanent cookie .......
   objCookie.Expires = DateTime.MaxValue;

            Response.Cookies.Add(objCookie);
           
 Response.Redirect("Default2.aspx");