When I try use ExportToWKB:
var wkbGeom = GeometryEngine.Instance.ExportToWKB(WkbExportFlags.WkbExportPolygon, geometry);
I get following error:
System.Exception: 'COMException: An unspecified error has occurred.'
There is mentioned "Does not support curves" in the documentation, but nothing about multiparts. So is it supposed to work on multiparts or not? I tried to create very simple multipart polygon with two squares and it does not work on it either.