/// <summary>
        /// Handler for the system Help command; launches the Revit contextual help with the right context and returns true
        /// so the parent doesn't launch its own help on top of ours
        /// </summary>
        /// <returns></returns>
        protected override bool OnContextHelp()
        {
            // launch help
            Autodesk.Revit.UI.ContextualHelp help = new Autodesk.Revit.UI.ContextualHelp(Autodesk.Revit.UI.ContextualHelpType.ContextId, "HID_EXPORT_IFC");
            help.Launch();

            return(true);
        }
        protected override bool OnContextHelp()
        {
            string contextIdName = null;

            if (m_SingleNodeSelection)
            {
                contextIdName = "IFC_EntityAndPredefinedType";
            }
            else
            {
                contextIdName = "IFC_EntitiesToExport";
            }

            // launch help
            Autodesk.Revit.UI.ContextualHelp help = new Autodesk.Revit.UI.ContextualHelp(Autodesk.Revit.UI.ContextualHelpType.ContextId, "HDialog_" + contextIdName);
            help.Launch();

            return(true);
        }