void mnuFunction_Opening(object sender, CancelEventArgs e)
{
BaseTreeListTag treeListTag = _mainForm.treeList.FocusedNode.Tag as BaseTreeListTag;
bool visible = (treeListTag.GetFunctionName().ToLower() == DefFun.DefIl.ToLower());
mniDescriptionAsComment.Visible = visible; //this menu item is only available for the function DefIL
toolStripSeparator_DefIL.Visible = visible;
}