Access the original geoprojection after the shapefile was reprojected?

Hi there:
A shapefile layer was added to the current map, and it was reprojected to the map’s geoprojection. When I tried to access the shapefile’s Geoprojection property, I got the map’s geoprojection instead of the shapefile’s. So the problem is how do I access the original geoprojection of the shapefile. I am using MapWinGIS v5.3.0 in C#.
By the way, if a shapefile layer in the current map is reprojected, the FileName property of the shapefile will be empty string. How to retrieve its source filename?
Thanks, guys!