ASPxClientGanttTaskEventArgs Class

<dx:ASPxGantt ID="Gantt" >
    <ClientSideEvents TaskClick="onGanttTaskClick" TaskDblClick="onGanttTaskDblClick" ... />
</dx:ASPxGantt>

function onGanttTaskClick(s, e) {
    if (e.key == 5) {
        //...
        e.cancel = true;
    }
}
function onGanttTaskDblClick(s, e) {
    if (e.key == 5) {
        //...
        e.cancel = true;
    }
}