C # Release the memory reprinted by COM Object Reference

ESRI. ArcGIS. display. istylegallery stycls = new
ESRI. ArcGIS. Framework. stylegalleryclass ()
ESRI. ArcGIS. display. istylegallery;
Int irefsleft = 0;
Do
{
Irefsleft = marshal. releasecomobject (stycls );
}
While (irefsleft> 0 );

From: http://bbs.esrichina-bj.cn/esri/viewthread.php? Tid = 119595 & extra = Page % 3d2

I have seen this in the help document. I would like to ask the author a question: how can we distinguish between COM objects and non-COM objects in AE? For example, istylegallery, istylegallerystorage, ienumstylegalleryitem, istylegalleryitem, istylegalleryitem, and istylegalleryclass interfaces are generally used to implement layer symbolic functions. Are these COM objects released after use?

Istylegalleryitem can be released without an error.
It seems that most interfaces starting with AE I are COM objects.

However, ifeaturecursor must be released frequently.