DropDownList控件的changed事件调用
DropDownList控件的SelectedIndexChanged和TextChanged事件调用必须首先把该控件的AutoPostBack属性设置为true,否则该事件在应用时无法自动触发!
<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True">
</asp:DropDownList>
<asp:DropDownList ID="DropDownList1" runat="server"
onselectedindexchanged="DropDownList1_SelectedIndexChanged"
ontextchanged="DropDownList1_TextChanged"
AutoPostBack="True">
</asp:DropDownList>