菜鸟学习《ASP.net2.0高级编程》时，调不出的一个例子，求救！
第十二章 使用ADO.net管理数据，程序清单12-1，想问的是：
1、自己觉得可能是ConfigurationManager.ConnectionStrings( "DSN_Northwind ").ConnectionString地方有问题，但不知如何修改；
2、如果想引用web.config中定义的数据连接字符串，应该如何修改？
源码如下：
<%@ Page Language= "VB "%>
<%@ Import Namespace= "System.Data " %>
<%@ Import Namespace= "System.Data.SqlClient " %>
<%@ Import Namespace= "System.Configuration " %>
<script runat= "server ">
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
If Not Page.IsPostBack Then
Dim MyConnection As SqlConnection
Dim MyCommand As SqlCommand
Dim MyReader As SqlDataReader
MyConnection = New SqlConnection()
MyConnection.ConnectionString = ConfigurationManager.ConnectionStrings( "DSN_Northwind ").ConnectionString
MyCommand = New SqlCommand()
MyCommand.CommandText = "SELECT TOP 3 * FROM CUSTOMERS "
MyCommand.CommandType = CommandType.Text
MyCommand.Connection = MyConnection
MyCommand.Connection.Open()
MyReader = MyCommand.ExecuteReader(CommandBehavior.CloseConnection)
gvCustomers.DataSource = MyReader
gvCustomers.DataBind()
MyCommand.Dispose()
MyConnection.Dispose()
End If
End Sub
</script>
<html>
<body>
<form id= "form1 " runat= "server ">
<div>
<asp:GridView ID= "gvCustomers " runat= "server ">
</asp:GridView>
</div>
</form>
</body>
</html>
[解决办法]
Object reference not set to an instance of an object.
对象未赋予实例！
可能是你的web.config字串写错，连接不上数据
[解决办法]
ConfigurationManager
-------------------------
需要引入System.Configruation命名空间
<%@ Import Namespace= "System.Configuration " %> 是不够的
在解决方案ＢＩＮ文件夹上点击右键，选择添加引用，在.net组件中往下拉滚动条，找到System.configruation点击确定，然后运行吧
