这是源代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace listbox
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (Page.IsPostBack)
            {
                Data ds = new Data();
                ds.Tables.Add("stu");
                ds.Tables["stu"].Columns.Add("stuNo",typeof(int));
                ds.Tables["stu"].Columns.Add("stuName",typeof (string));
                ds.Tables["stu"].Columns.Add("stuScore",typeof(int));
                ds.tables["stu"].Rows.Add(new object[] { 1, "张一", 100 });
                ds.tables["stu"].Rows.Add(new object[] { 1, "王二", 100 });
                ds.tables["stu"].Rows.Add(new object[] { 1, "李珊", 100 });
                ds.tables["stu"].Rows.Add(new object[] { 1, "赵四", 100 });
                ds.tables["stu"].Rows.Add(new object[] { 1, "周五", 100 });
                ds.tables["stu"].Rows.Add(new object[] { 1, "钱六", 100 });
                this.ListBox1.DataSource = ds.Tables["stu"];
                this.ListBox1.DataValueField = "stuNo";
                this.ListBox1.DataTextField = "stuName";
                this.ListBox1.DataBind();

            }
        }

        protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            this.Label1.Text = "你选择的学生是：学号"+this.ListBox1.SelectedValue.ToString()+"姓名"+this.ListBox1.SelectedItem.Text.ToString ();
        }
    }
}

找不到Data类型,需要using一下

把Data ds = new Data();换成DataSet ds= new DataSet()； 然后引用一个Data.SqlClient命名空间，这样的改动可以么？

要用datatable dt=new data(),using system.data;
Data.SqlClient是链接数据库时用的