protected internal int ToggleShowAllFiles()
        {
            if (this.ProjectMgr == null || this.ProjectMgr.IsClosed)
            {
                return((int)OleConstants.OLECMDERR_E_NOTSUPPORTED);
            }

            using (XHelperMethods.NewWaitCursor())
            {
                this.showAllFilesEnabled = !this.showAllFilesEnabled; // toggle the flag

                if (this.showAllFilesEnabled)
                {
                    XProjectMembers.AddNonMemberItems(this);
                }
                else
                {
                    XProjectMembers.RemoveNonMemberItems(this);
                }
            }

            return(VSConstants.S_OK);
        }