CheckedListBox的读取Value值问题

<%@ Page Language="C#" %>
<html>
<head><script language="C#" runat="server">   void Check_Clicked(Object sender, EventArgs e) 
   {
      Message.Text = "Selected Item(s):<br><br>";
      for (int i=0; i<checkboxlist1.Items.Count; i++)
      {
         if (checkboxlist1.Items[i].Selected)
            Message.Text += checkboxlist1.Items[i].Text + "<br>";
      }
   }</script>
 
</head>
<body>
   
   <form action="checkboxlist.aspx" method="post" runat="server">
 
      <h3>CheckBoxList Example</h3>      <asp:CheckBoxList id="checkboxlist1" 
           AutoPostBack="True"
           CellPadding="5"
           CellSpacing="5"
           RepeatColumns="2"
           RepeatDirection="Vertical"
           RepeatLayout="Flow"
           TextAlign="Right"
           OnSelectedIndexChanged="Check_Clicked"
           runat="server">
 
         <asp:ListItem>Item 1</asp:ListItem>
         <asp:ListItem>Item 2</asp:ListItem>
         <asp:ListItem>Item 3</asp:ListItem>
         <asp:ListItem>Item 4</asp:ListItem>
         <asp:ListItem>Item 5</asp:ListItem>
         <asp:ListItem>Item 6</asp:ListItem>
 
      </asp:CheckBoxList>
 
      <br><br>      <asp:label id="Message" runat="server"/>
             
   </form>
          
</body>
</html>