/// <summary>
/// Identifies each exterior ring as separate part, containing all its interior rings
/// </summary>
/// <param name="polygon"></param>
/// <returns></returns>
private static IEnumerable <GeometryPart> GetPolygonExteriorRingParts(
[NotNull] IPolygon4 polygon)
{
// for all interior rings, assign to exterior ring's part
// all exterior rings, add them to result if not yet added
var partsByExteriorRing = new Dictionary <IRing, GeometryPart>();
var geometryCollection = (IGeometryCollection)polygon;
for (var i = 0; i < geometryCollection.GeometryCount; i++)
{
var ring = (IRing)geometryCollection.Geometry[i];
if (ring.IsExterior)
{
partsByExteriorRing.Add(ring, new GeometryPart(ring));
}
else
{
IRing exteriorRing = polygon.FindExteriorRing(ring);
Assert.NotNull("No exterior ring found for inner ring");
GeometryPart part;
if (!partsByExteriorRing.TryGetValue(exteriorRing, out part))
{
part = new GeometryPart(exteriorRing);
partsByExteriorRing.Add(exteriorRing, part);
}
part.AddInnerRingGeometry(ring);
}
}
return(partsByExteriorRing.Values);
}
