对绑定数据进行修改时出现问题！！
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Configuration;

namespace 学生管理系统
{
    public partial class Modify : Form
    {
        string no;
        string cno;
        public string No
        {
            get
            {
                return no;
            }
            set
            {
                no = value;
            }
        }
        public string CNo
        {
            get
            {
                return cno;
            }
            set
            {
                cno = value;
            }
        }
        SqlDataAdapter adapter = null;
        DataSet dataset = new DataSet();
        SqlDataAdapter adapter1 = null;
        DataSet dataset1 = new DataSet();
        SqlDataAdapter adapter2 = null;
        DataSet dataset2 = new DataSet();
        string connstr = ConfigurationManager.ConnectionStrings["ConnStr1"].ConnectionString;
        public Modify()
        {
            InitializeComponent();
        }

        private void Modify_Load(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(connstr);
            
   &nbs