这个是读取摸个表里所有数据，我只想读取这个表的前两条，应该怎么改？

我试着改：        SqlCommand cmd = new SqlCommand("select top 2 CategoryID from Categories1", conn); 但是测试结果是不对的，请高手帮看下，为什么这样写不行，应该怎么写

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //创建SqlConnection对象
        SqlConnection conn = new SqlConnection("server=(local);database=fangdawei;uid=123456;pwd=123456");
        //打开数据库连接
        conn.Open();
        //创建SqlCommand对象
        SqlCommand cmd = new SqlCommand("select * from Categories1", conn);
        //接收ExecuteReader方法返回的SqlDataReader对象
        SqlDataReader sdr = cmd.ExecuteReader();
        //输出表格
        Response.Write("<table border=1 align='center' ");
        Response.Write("<tr><th>编号</th><th>图书名称</th><th>图书描述</th></tr>");
        //显示学生信息
        while (sdr.Read())
        {
            Response.Write("<tr>");
            Response.Write("<td align='center'>" + sdr["CategoryID"].ToString() + "</td>");
            Response.Write("<td align='center'>" + sdr["CategoryName"].ToString() + "</td>");
            Response.Write("<td align='left'>" + sdr["Description"].ToString() + "</td>");
            Response.Write("</tr>");
        }
        Response.Write("</table>");
        sdr.Close();
        conn.Close();
    }
}