为什么我总是在Conn.Open();处总有"未将对象引用应用到对象的实例"

using System;
using System.Collections;
using
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

namespace xsw99
{
    /// <summary>
    /// showcourse 的摘要说明。
    /// </summary>
    public class showcourse : System.Web.UI.Page
    {
        protected System.Web.UI.WebControls.DataGrid DataGrid1;
        
        
        public string getrs;
        public int bh;
        public string km;
        
        private void Page_Load(object sender, System.EventArgs e)
        {
            bind();
        }
    void bind()
        {
    SqlConnection conn=new SqlConnection("server=(local);uid=sa;pwd=0;database=新思维");
    string sql="select top 10 * from kcb order by posttime desc";
    SqlCommand cmd=new SqlCommand(sql,conn);
            
    conn.Open();
            
    DataGrid1.DataSource=cmd.ExecuteReader();
    DataGrid1.DataBind();
    conn.Close();

    }
小弟刚学.net没多久 还请大家多多直教!