急急急急 “ASP.leftroom_leftroom_aspx”不包含“DataList1_ItemDataBound”的定义，并且找不到可接受类

Question

我要把datalist中的label中的只取出来，但是老是提示“错误 CS1061: “ASP.leftroom_leftroom_aspx”不包含“DataList1_ItemDataBound”的定义，并且找不到可接受类型为“ASP.leftroom_leftroom_aspx”的第一个参数的扩展方法“DataList1_ItemDataBound”(是否缺少 using 指令或程序集引用?)”，我已经定义了了 啊，
代码如下：
<asp:DataList ID="DataList1" runat="server" DataKeyField="房间号" 
                                            DataSourceID="SqlDataSource1" RepeatColumns="4" RepeatDirection="Horizontal" 
                                            Width="1016px" onselectedindexchanged="DataList1_SelectedIndexChanged" 
                                            BorderColor="#3399FF" onitemcommand="DataList1_ItemCommand" 
                                            onitemdatabound="DataList1_ItemDataBound"  >
我已经定义了onitemdatabound="DataList1_ItemDataBound"了呀，，，原因在哪里呢？
                                           
                  

Answer 1

定义onitemdatabound="DataList1_ItemDataBound"有什么用，你的cs文件中必须有DataList1_ItemDataBound的实现代码

Answer 2

我弄了以后报这个错是怎么回事啊
异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。源错误:
行 56:     protected void DataList1_ItemDataBound(object sender, DataListItemEventArgs e)
行 57:     {
行 58:         Label 房间号Label = e.Item.FindControl("房间号") as Label; string restrant_ID = 房间号Label.Text;
行 59:     }
行 60: }
后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Data.SqlClient;using CrystalDecisions.Shared;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Web;public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {       
    }
    
   
    protected void SqlDataSource1_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {    }
    protected void Button3_Click(object sender, EventArgs e)
    {
        if (Session["uid"] == null)
        {
            RegisterStartupScript("", "<script>alert('你尚未登录!')</script>");
        }
        else
        {
                       Response.Redirect("http://localhost:49261/HMSTRYtry/Order/Order.aspx?restrant_ID=");
            
 
        }    }    protected void DataList1_ItemCommand(object source, DataListCommandEventArgs e)
    {
        
    }
    protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
    {    }
    protected void DataList1_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        Label 房间号Label = e.Item.FindControl("房间号") as Label; string restrant_ID = 房间号Label.Text;
    }
}

Answer 3

 后台版定代码：1、protected void DataList1_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        Label 房间号Label = e.Item.FindControl("房间号Label") as Label;        string restrant_ID = 房间号Label.Text.ToString();
    }
2.protected void Button3_Click(object sender, EventArgs e)
    {
        if (Session["uid"] == null)
        {
            RegisterStartupScript("", "<script>alert('你尚未登录!')</script>");
        }
        else
        {
            Button 房间号Lable = (Button)sender;
            Session["房间号"] = 房间号Lable.CommandArgument;
            Response.Redirect("http://localhost:49261/HMSTRYtry/Order/Order.aspx?id=xx");        }