open the modal open for errors asp: ValidationSummary

Good afternoon,
I am building a form of e-mailing.
I create the part of asp: ValidationSummary and want only opens the modal form is open to errors in the asp: ValidationSummary.

<ajaxToolkit:ModalPopupExtender 
    ID="MPErros" 
    runat="server" 
    TargetControlID="btEnviar"
    PopupControlID="ModalErros" 
    DropShadow="false" 
    CancelControlID="BotaoCancelar"/><asp:Panel ID="ModalErros" runat="server" Style="display:none;" CssClass="modal"><asp:ValidationSummary
        ShowMessageBox="False"
        ID="VS_Consultas"
        runat="server"
        DisplayMode="List"
        ValidationGroup="Erro" />                    <asp:LinkButton 
            ID="BotaoCancelar" 
            runat="server"
            CssClass="close"
            CausesValidation="false"><img src="Imagens/fechar.png" runat="server" title="Fechar" style="text-align:center;" /></asp:LinkButton></asp:Panel>

When there is no error in the ValidationSummary it opens the modal open but without the errors but I do not want that to happen