cmd.Parameters.Add("@PWD",SqlDbType.VarChar,20);

         cmd.Parameters["@ID"].Value=txtName.Text;

         cmd.Parameters["@PWD"].Value=txtPwd.Text;

         conn.Open();

         using (SqlDataReader dr = cmd.ExecuteReader())

         {

             if(dr.Read())

             {

                bool NotOL=true;

                for(int i=0;i<Application.Count;i++)

                {

                   if(Application[Application.GetKey(i).ToString()].ToString()==dr["UserID"].ToString())

                   NotOL=false;

                }

                if(NotOL)

                {

                   Application[Session.SessionID.ToString()]=dr["UserID"].ToString();

                   Application["OL_UserCount"]=(int)Application["OL_UserCount"]+1;

                   Session["UserName"]=dr["UserName"].ToString();//Sessions
                   Response.Redirect("./main/main.aspx");

                }

                else

                   message.Text="已经登陆";

             }