Using LinkButton to validate Validation Group

Question

In a .Net WebForm I have a Button working fine to validate a ValidationGroup using the following:

<asp:Button ID="Button1" runat="server" Text="Validate" ValidationGroup="ClientConditions" CausesValidation="true"/>

However if I use a LinkButton in the same way the validate does not work:

<asp:LinkButton ID="LinkButton1" runat="server" Text="AgainValidate" ValidationGroup="ClientConditions" CausesValidation="true">LinkButton</asp:LinkButton>

is there something I'm missing?