public void GetExteriorRings(Polygon inputPolygon)
{
if (inputPolygon == null || inputPolygon.IsEmpty)
return;

// polygon part count
int partCount = inputPolygon.PartCount;
// polygon exterior ring count
int numExtRings = inputPolygon.ExteriorRingCount;
// get set of exterior rings for the polygon
IList<Polygon> extRings = inputPolygon.GetExteriorRings();

// test each part for "exterior ring"
for (int idx = 0; idx < partCount; idx++)
{
bool isExteriorRing = inputPolygon.IsExteriorRing(idx);
}
}