Using validators from code behind

Hi All,
a stupid question.
If you see the code below, I would like to use the
<asp:Literal runat="server" ID="FailureText" /> in order to show all validators messages and in order to make the  ErrorMessage.Visible = True applying when the textbox is empy and when the user is not entering a valid email address:
<asp:PlaceHolder runat="server" ID="ErrorMessage" Visible="false"> <p class="text-danger"> <asp:Literal runat="server" ID="FailureText" /> </p> </asp:PlaceHolder> <asp:Label runat="server" AssociatedControlID="Email" CssClass="col-md-2 control-label">Email address</asp:Label><br /><br /> <asp:TextBox runat="server" ID="Email" CssClass="txtbox" TextMode=&qu ...