AutoPostBack已设为TRUE，DropDownList改变下拉列表内容为什么没有反应？

Question

我把代码贴出来,请帮我修改正确，谢谢！<script language="c#" runat="server">
void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
{        
   label1.Text = "You selected " + DropDownList1.SelectedItem.Text;
}
</script>
......
<form runat="server">
      <asp:DropDownList id="DropDownList1" 
          AutoPostBack="true"  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:DropDownList>
<asp:label ID="label1" runat="server"/>
</form>

Answer 1

<asp:DropDownList id="DropDownList1" 
          AutoPostBack="true"  runat="server" OnChange="DropDownList1_SelectedIndexChanged">

Answer 2

你都没加事件怎么能有反映呢：
<asp:DropDownList id="DropDownList1" AutoPostBack="true"  runat="server" OnSelectedIndexChanged ="DropDownList1_SelectedIndexChanged">

Answer 3

在DropDownList属性中，选择时间，然后选择OnSelectedIndexChanged，双击，就会出现这个事件的函数，然后在函数中写如下代码 ——
          label1.Text = "You selected " + DropDownList1.SelectedItem.Text;

Answer 4

<asp:DropDownList id="zmYear" runat="server" AutoPostBack="True">
<asp:ListItem Value="1999">1999</asp:ListItem>
<asp:ListItem Value="2000">2000</asp:ListItem>
</asp:DropDownList>
属性窗口在加入OnSelectedIndexChanged事件

Answer 5

<asp:DropDownList id="DropDownList1" 
          AutoPostBack="true"  runat="server" OnChange="DropDownList1_SelectedIndexChanged">