I have another interesting question for you.
I have data with unknown coordinate system. When I add this data using a standard tool(File->Add Data) in ArcMap, a warning dialog appears. It looks like:
But this dialog didn't appears if I add data programmatically using arcobjects. Is there a way to show this dialog, if I add layers programmatically?
P.S. I found DatumCheckerClass, but that's not what I need.