怎样用DataGrid显示数据

<%@ Import namespace="System.Data"%>
<%@ Import namespace="System.Data.SqlClient"%>
<HTML>
<HEAD>
<title>DataGrid</title>
</HEAD>
<body>
<h3>DataGrid</h3>
<form runat="server">
<asp:datagrid ID="teacher1" runat="server" AutoGenerateColumns="true">
<Columns>
<asp:BoundColumn DataField="tacherNo" HeaderText="Tacher No" DataFormatString="#{0:D7}"></asp:BoundColumn>
<asp:BoundColumn DataField="tacName" HeaderText="Tacher Name" DataFormatString="#{0:d}"></asp:BoundColumn>
</Columns>
</asp:datagrid>
</form>
</body>
</HTML>
<script language="C#" runat="server">
 private void Page_Load(object sender, System.EventArgs e)
{       
           String strConnection=ConfigurationSettings.AppSettings["result"];
   SqlConnection objConnection=new SqlConnection(strConnection);
   String strSQL="SELECT * FROM teacher";
   SqlDataAdapter objAdapter=new SqlDataAdapter(strSQL,objConnection);
   DataSet objDataSet=new DataSet();
   objAdapter.Fill(objDataSet);
   objConnection.Close();
   teacher1.DataSource=objDataSet;
   teacher1.DataBind();
}
</script>调试错误：ConnectionString 属性尚未初始化