public void changepassword(User_db udb)
        {
            string        query = String.Format("update [signup] set [Password]='{0}' where [Username]='{1}'", udb.Password, udb.Username);
            Businesslogic BL    = new Businesslogic();

            BL.Nonquery(query);
        }
        public void DeleteUser(User_db udb)
        {
            string        query = String.Format("Delete from signup where Username='******'", udb.Username);
            Businesslogic BL    = new Businesslogic();

            BL.Nonquery(query);
        }
        public void Insertuser(User_db udb)
        {
            string query = String.Format("insert into signup values ('{0}','{1}','{2}','{3}')",
                                         udb.Username, udb.Names, udb.Password, udb.Usertype);
            Businesslogic BL = new Businesslogic();

            BL.Nonquery(query);
        }
        public void Addcourse(User_db udb)
        {
            string query = String.Format("insert into courses values ('{0}','{1}','{2}')",
                                         udb.Names, udb.Fees, udb.Course);
            Businesslogic BL = new Businesslogic();

            BL.Nonquery(query);
        }