什么有关问题

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Data.Linq;public partial class _Default : System.Web.UI.Page{    GuestBookDataContext ctx = new GuestBookDataContext("server=.;database=JumbotOA;uid=sa;pwd=sa!#%246");    protected void Page_Load(object sender, EventArgs e)    {        if (!IsPostBack)        {            SetBind();        }    }    private void SetBind()    {        rpt_Message.DataSource = from c in ctx.tbGuestBook orderby c.PostTime ascending select new { c.UserName, c.PostTime, c.Message, c.IsReplied, c.Reply };        rpt_Message.DataBind();    }    protected void btn_SendMessage_Click(object sender, EventArgs e)    {        tbGuestBook gb = new tbGuestBook();               gb.UserName = tb_UserName.Text;        gb.Message = tb_Message.Text;        gb.IsReplied = false;        gb.PostTime = DateTime.Now;        ctx.tbGuestBook.Add(gb);        ctx.SubmitChanges();        SetBind();    }}