How to add MaskedEditExtender in Dot Net

This is MaskedEditExtender for Date

<asp:maskededitextender ID="MaskedEditExtender1" runat="server"
        Mask="99/99/9999" MaskType="Date" TargetControlID="txtEffectiveDate"
        PromptCharacter="_"> </asp:maskededitextender>


<asp:calendarextender ID="CalendarExtender1" TargetControlID="txtEffectiveDate"
        Format="dd/MM/yyyy" runat="server">
</asp:calendarextender>