我做了一个学生信息的删除修改 可是就是编辑删除失败 哪位大虾可以帮小妹指点一下？？？？？[em18]


<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<script runat="server">
SqlConnection Conn;
protected void Page_Load(Object Src, EventArgs E ) {
    
    Conn=new SqlConnection("server=127.0.0.1;database=jiaoshi;uid=sa;pwd='1'"); 
    Conn.Open();
    if (!IsPostBack) BindGrid();
}
void DataGrid_Edit(Object sender,DataGridCommandEventArgs E){
   dg.EditItemIndex = (int)E.Item.ItemIndex;
   BindGrid();
}
void DataGrid_Cancel(Object sender,DataGridCommandEventArgs E){
   dg.EditItemIndex = -1;
   BindGrid();
}
void DataGrid_Update(Object sender,DataGridCommandEventArgs E){
   String strSQL = "UPDATE stu_inf SET "+
         "姓名='"+((TextBox)E.Item.Cells[3].Controls[0]).Text
         +"',联系方式="+((TextBox)E.Item.Cells[4].Controls[0]).Text
         +" where 学号="+dg.DataKeys[(int)E.Item.ItemIndex];
   SqlCommand cm = new SqlCommand(strSQL,Conn);

   try    {
      cm.ExecuteNonQuery();
      Message.InnerHtml="<b>编辑成功</b>";
      // 退出编辑状态
      dg.EditItemIndex=-1;
   }
   catch (SqlException) {
      Message.InnerHtml="编辑失败";
      Message.Style["color"]="red";
   }
   cm.Connection.Close();
   // 更新DataGrid
   BindGrid();
}
// 处理删除事件
public void DataGrid_Delete(Object sender,DataGridCommandEventArgs E){
   String strSQL="DELETE FROM stu_inf WHERE 学号="
    + dg.DataKeys[(int)E.Item.ItemIndex];
  SqlCommand cm = new SqlCommand(strSQL,Conn);
   
   try {
      cm.ExecuteNonQuery();
      Message.InnerHtml = "<b>删除成功</b>";
   }
   catch (SqlException){
      Message.InnerHtml = "<b>删除失败</b>";
      Message.Style["color"]="red";
   }
   Conn.Close();
   BindGrid();
}
public void BindGrid() {
   SqlDataAdapter da=new SqlDataAdapter("select * from stu_inf",Conn);
   DataSet ds = new DataSet();
   da.Fill(ds);
   dg.DataSource=ds;
   dg.DataBind();
}
</script>
<style type="text/css">
<!--
.STYLE1 {
    font-size: 12px;
    font-weight: bold;
}
body {
    background-color: #aaaaCC;
}
-->
</style>
<body style="font: 10pt verdana">
<form runat="server">
  <asp:DataGrid id="dg" runat="server"
          Width="400" BackColor="#ccccff" 
          BorderColor="black" ShowFooter="false" 
          CellPadding=3 CellSpacing="0"
          Font-Name="Verdana" Font-Size="8pt"
          HeaderStyle-BackColor="#aaaadd"
          OnEditCommand="DataGrid_Edit"
          OnCancelCommand="DataGrid_Cancel"
          OnUpdateCommand="DataGrid_Update"
          OnDeleteCommand="DataGrid_Delete"
          DataKeyField="学号"
          AutoGenerateColumns="false"
          MaintainState="false">
     <Columns>
<asp:EditCommandColumn EditText="编辑" CancelText="取消" 
UpdateText="更新" ItemStyle-Wrap="false"/>
<asp:ButtonColumn Text="删除" CommandName="Delete" ItemStyle-Wrap="false"/>
<asp:BoundColumn HeaderText="学号" DataField="学号" ReadOnly="True"/>
<asp:BoundColumn HeaderText="姓名" DataField="姓名" />
<asp:BoundColumn HeaderText="联系方式" DataField="联系方式" />
</Columns>
</asp:DataGrid> 
  <span id="Message" MaintainState="false"  
        style="font: arial 11pt;" runat="server"/>
</form>