小弟问一个关于dataGrid1 的问题 大家帮帮忙吧 困扰小弟好几天了....
using   System;
using   System.Drawing;
using   System.Collections;
using   System.ComponentModel;
using   System.Windows.Forms;
using   System.Data;
using   System.Data.OleDb;


namespace   WindowsApplication1
{
///   <summary>
///   Form5   的摘要说明。
///   </summary>
public   class   Form5   :   System.Windows.Forms.Form
{
private   System.Windows.Forms.Label   label1;
private   System.Windows.Forms.TextBox   textBox1;
private   System.Windows.Forms.Button   button1;
private   System.Windows.Forms.Button   button2;
private   DataSet   ds=new   DataSet();
private   string   Afile;
private   OleDbConnection   Conn;
//private   System.Windows.Forms.Button   updata_button;
//private   System.Windows.Forms.Button   del_botton;
private   string   sss= " ";

///   <summary>
///   必需的设计器变量。
///   </summary>
private   System.ComponentModel.Container   components   =   null;

public   Form5()
{
//
//   Windows   窗体设计器支持所必需的
//
InitializeComponent();

//
//   TODO:   在   InitializeComponent   调用后添加任何构造函数代码
//
}

///   <summary>
///   清理所有正在使用的资源。
///   </summary>
protected   override   void   Dispose(   bool   disposing   )
{
if(   disposing   )
{
if(components   !=   null)
{
components.Dispose();
}
}
base.Dispose(   disposing   );
}

#region   Windows   窗体设计器生成的代码
///   <summary>
///   设计器支持所需的方法   -   不要使用代码编辑器修改
///   此方法的内容。
///   </summary>
private   void   InitializeComponent()
{
this.label1   =   new   System.Windows.Forms.Label();
this.textBox1   =   new   System.Windows.Forms.TextBox();
this.button1   =   new   System.Windows.Forms.Button();
this.button2   =   new   System.Windows.Forms.Button();
this.SuspendLayout();
//  
//   label1
//  
this.label1.Font   =   new   System.Drawing.Font( "宋体 ",   15F,   System.Drawing.FontStyle.Bold,   System.Drawing.GraphicsUnit.Point,   ((System.Byte)(134)));
this.label1.Location   =   new   System.Drawing.Point(40,   48);
this.label1.Name   =   "label1 ";
this.label1.Size   =   new   System.Drawing.Size(376,   40);
this.label1.TabIndex   =   0;
this.label1.Text   =   "请输入您要查询的学生选课情况的学号 ";
//  
//   textBox1
//  
this.textBox1.Location   =   new   System.Drawing.Point(152,   112);
this.textBox1.Name   =   "textBox1 ";
this.textBox1.Size   =   new   System.Drawing.Size(184,   21);
this.textBox1.TabIndex   =   1;
this.textBox1.Text   =   " ";
this.textBox1.TextChanged   +=   new   System