RequiredFieldValidator下拉框验证

 

                         <asp:DropDownList id="DropDownList1" runat="server">
                               <asp:ListItem Value="请选择">请选择</asp:ListItem>
                               <asp:ListItem Value="1">北京</asp:ListItem>
                               <asp:ListItem Value="2">上海</asp:ListItem>
                           </asp:DropDownList>
                           <asp:RequiredFieldValidator id="rfvCity"
                               runat="server" ErrorMessage="你必须选择一个城市"
                               ControlToValidate="DropDownList1" InitialValue="请选择" />