validation with ajax filter

  
 <asp:TextBox ID="txtMessage" runat="server" TextMode="MultiLine" autocomplete="off"  TabIndex="15"></asp:TextBox>
                                    </div>
                                    <div class="errormsg_contact">
                                        <asp:RequiredFieldValidator ID="rfvYourMessage" runat="server" ControlToValidate="txtMessage"
                                Display="Dynamic" ErrorMessage="Please enter your message" ValidationGroup="SUBMIT"
                                SetFocusOnError="true"> </asp:RequiredFieldValidator>

                                <cc1:FilteredTextBoxExtender ID="FilteredTextBoxExtender3" runat="server"
                                FilterType="Custom, Numbers, UppercaseLetters, LowercaseLetters" ValidChars=" ,./\()_" TargetControlID="txtMessage"> </cc1:FilteredTextBoxExtender>

                                        <asp:RegularExpressionValidator ID="rvtxtMessage" runat="server" ControlToValidate="txtMessage"
                                Display="Dynamic" ErrorMessage="Message contains minuman 5 maximum 1000 characters with or without space"
                                ValidationExpression="[,./\()_-a-zA-z0-9 ]{5,1000}" ValidationGroup="SUBMIT"
                                SetFocusOnError="true" />