I have a start date field:
<asp:TextBox ID="txtStartDate" Width="150px" TabIndex="25" TextMode="Date" runat="server" MaxLength="10"></asp:TextBox>
<ajaxToolkit:CalendarExtender ID="txtStartDate_CalendarExtender" Format="MM/dd/yyyy"
runat="server" Enabled="True" TargetControlID="txtStartDate" PopupButtonID="imgCalendarStart">
</ajaxToolkit:CalendarExtender>
<asp:RequiredFieldValidator ID="rfvStartDate" runat="server" ControlToValidate="txtStartDate" EnableClientScript="false"
ErrorMessage="Please enter a valid value in the Start Date field." Display="Dynamic">*</asp:RequiredFieldValidator ...
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