<asp:TextBox ID="TextBox20" runat="server" Width="100px"></asp:TextBox>
                                                    <asp:MaskedEditExtender ID="MaskedEditExtender3" runat="server" 
                                                        CultureAMPMPlaceholder="" CultureCurrencySymbolPlaceholder="" 
                                                        CultureDateFormat="" CultureDatePlaceholder="" CultureDecimalPlaceholder="" 
                                                        CultureThousandsPlaceholder="" CultureTimePlaceholder="" Enabled="True" 
                                                        ErrorTooltipEnabled="True" Mask="99/99/9999" MaskType="Date" 
                                                        TargetControlID="TextBox20">
                                                    </asp:MaskedEditExtender>
                   <asp:MaskedEditValidator ID="MaskedEditValidator2"
                   runat="server" ControlExtender="MaskedEditExtender3"
                   ControlToValidate="TextBox20" 
                   IsValidEmpty="False" MaximumValue="01/01/2099" MinimumValue="01/01/1900"
                   EmptyValueMessage="Inserire data!"
                   MaximumValueMessage="Data massima inseribile 01/01/2099"
                   InvalidValueBlurredMessage="Data non valida!"
                   MinimumValueMessage="Data minima 01/01/1900"
                   EmptyValueBlurredText="*"
                   ToolTip="Inserire una data compresa tra 01/01/1900 e 01/01/2099" ErrorMessage="MaskedEditValidator2"></asp:MaskedEditValidator>