验证控件验证DropDownList

  <tr>

           <td class="caption td_caption">

                 免疫程序：

          </td>

           <td class="txtbox td_textbox">

                <asp:DropDownList ID="ddlMYCX" runat="server" Width="200px" AutoPostBack="true" AppendDataBoundItems="true"

                                                    OnSelectedIndexChanged="ddlMYCX_SelectedIndexChanged">

                 </asp:DropDownList>

                <asp:CompareValidator ID="CompareValidator1" runat="server" Display="None" ValidationGroup="ValidationGroup1"

                                                    ControlToValidate="ddlMYCX" Operator="NotEqual" Type="Integer " ValueToCompare="0"

                                                     ErrorMessage="<span class='ErrorMessage'>必须输入选择“免疫程序”</span>"></asp:CompareValidator>

                 <ajaxToolkit:ValidatorCalloutExtender runat="Server" ID="Vcompare" TargetControlID="CompareValidator1"

                                                    HighlightCssClass="validatorCalloutHighlight" />

              </td>

 </tr>