membership change password and Required field validator with Update panel

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ASP.NET

Ajax

UpdatePanel

hello,
i have problem in asp.net membership change password in update panel.
my probelm similar this post:
Required field validator with Update panel[^]

The first when i fill textbox with wrong dada error message was show:

Password incorrect or New Password invalid. New Password length minimum: 7. Non-alphanumeric characters required: 1.

but For the second time i do the same thing again, but RequiredFieldValidator is fire and star was show near in textbox and textbox is refreshed (textbox value deleted).
how i can solve this problem?

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:ChangePassword ID="ChangePassword1" runat="server">
            <ChangePasswordTemplate>
                <table cellpadding="1" cellspacing="0" style="border-collapse:collapse;">
                    <tr>
                        <td>
                            <table cellpadding="0">
                                <tr>
                                    <td align="center" colspan="2">Change Your Password</td>
                                </tr>
                                <tr>
                                    <td align="right">
                                        <asp:Label ID="CurrentPasswordLabel" runat="server" AssociatedControlID="CurrentPassword">Password:</asp:Label>
                                    </td>
                                    <td>
                                        <asp:TextBox ID="CurrentPassword" runat="server" TextMode="Password"></asp:TextBox>
                                        <asp:RequiredFieldValidator ID="CurrentPasswordRequired" runat="server" ControlToValidate="CurrentPassword" ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="ChangePassword1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="right">
                                        <asp:Label ID="NewPasswordLabel" runat="server" AssociatedControlID="NewPassword">New Password:</asp:Label>
                                    </td>
                                    <td>
                                        <asp:TextBox ID="NewPassword" runat="server" TextMode="Password"></asp:TextBox>
                                        <asp:RequiredFieldValidator ID="NewPasswordRequired" runat="server" ControlToValidate="NewPassword" ErrorMessage="New Password is required." ToolTip="New Password is required." ValidationGroup="ChangePassword1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="right">
                                        <asp:Label ID="ConfirmNewPasswordLabel" runat="server" AssociatedControlID="ConfirmNewPassword">Confirm New Password:</asp:Label>
                                    </td>
                                    <td>
                                        <asp:TextBox ID="ConfirmNewPassword" runat="server" TextMode="Password"></asp:TextBox>
                                        <asp:RequiredFieldValidator ID="ConfirmNewPasswordRequired" runat="server" ControlToValidate="ConfirmNewPassword" ErrorMessage="Confirm New Password is required." ToolTip="Confirm New Password is required." ValidationGroup="ChangePassword1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="center" colspan="2">
                                        <asp:CompareValidator ID="NewPasswordCompare" runat="server" ControlToCompare="NewPassword" ControlToValidate="ConfirmNewPassword" Display="Dynamic" ErrorMessage="The Confirm New Password must match the New Password entry." ValidationGroup="ChangePassword1"></asp:CompareValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="center" colspan="2" style="color:Red;">
                                        <asp:Literal ID="FailureText" runat="server" EnableViewState="False"></asp:Literal>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="right">
                                        <asp:LinkButton ID="ChangePasswordPushButton" runat="server"  CommandName="ChangePassword" Text="Change Password" ValidationGroup="ChangePassword1" />
                                    </td>
                                    <td>
                                        <asp:Button ID="CancelPushButton" runat="server" CausesValidation="False" CommandName="Cancel" Text="Cancel" />
                                    </td>
                                </tr>
                            </table>
                        </td>
                    </tr>
                </table>
            </ChangePasswordTemplate>
        </asp:ChangePassword>
    </ContentTemplate>
</asp:UpdatePanel>
<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
    <ProgressTemplate>
        <img src="../Static/Css/Images/loading.gif" />now connecting to the server ...
    </ProgressTemplate>
</asp:UpdateProgress>