ASP.NET hidden field don't get correct value

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ASP.NET

Javascript

Hi, I've got a question for you,

I've got three buttons, i want the ID of the last clicked button in my code behind.

This is actually don't work:

$(function () {
    $('.btn').click(function () {
        $('.btn').attr('class', 'btn btn-default');
        $(this).attr('class', 'btn btn-primary');
        $("#<%=hfCb.ClientID%>").val($(this).attr('ID')); //hfCb is a hiddenfield
    });
});

<button  runat="server" id="btnFiltreLeft" type="button" class="btn btn-default"  önserverclick="btnFiltre_Click">Réceptionnés</button>
<button  runat="server" id="btnFiltreCenter" type="button" class="btn btn-default"  önserverclick="btnFiltre_Click">Validés</button>
<button  runat="server" id="btnFiltreRight" type="button" class="btn btn-default"  önserverclick="btnFiltre_Click">Tous</button>

btnFiltre_Click must be called here. In console I can see that the hidden field has the correct value but not in my code behind.

Protected Sub btnFiltre_Click(sender As Object, e As EventArgs)
    Debug.WriteLine(hfCb.Value)
End Sub

I've got a workaround, if I remove all the

onserverclick="btnFiltre_Click"

and do this in the JS

$(function () {
    $('.btn').click(function () {
        $('.btn').attr('class', 'btn btn-default');
        $(this).attr('class', 'btn btn-primary');
        $("#<%=hfCb.ClientID%>").val($(this).attr('ID')); //hfCb is a hiddenfield
        __doPostBack('ctl00$ContentPlaceHolder1$btnFiltre', "");
    });
});

I got the correct value in the code behind. But I want to know why I wasn't, is it due to the lyfecycle or what?