How split multi-part polygons, and keep holes, without geoprocessing tools?

[Mikael-J]

Hi,

I'm trying to loop over the features in a feature class and split each mulit-part polygon into single-part polygons. I don't want to use any geoprocessing tools. The problem is that the code below gives me each polygon part, but without the holes. I want to split the multi-part polygons but keep any polygon holes. Any ideas?

IFeatureClass inFc = // Input feature class

IFeatureClass outFc = // Ouput feature class

IFeature ftr;

IFeatureCursor cur = inFc.Search(null, true);

while ((ftr = cur.NextFeature()) != null)

{

// Get spatial reference from orginal feature

ISpatialReference spRef = ftr.ShapeCopy.SpatialReference;

object obj = Type.Missing;

IGeometryBag geomBag = ((IPolygon4)ftr.ShapeCopy).ExteriorRingBag;

IGeometryCollection coll = geomBag as IGeometryCollection;

for (int i = 0; i < coll.GeometryCount; i++)

{

IFeature newFtr = outFc.CreateFeature();

IGeometryCollection geomColl = new PolygonClass();

IGeometry geom = coll.get_Geometry(i);

geom.SpatialReference = spRef;

geomColl.AddGeometry(geom, ref obj, ref obj);

geomColl.GeometriesChanged();

IGeometry geom2 = (IPolygon)geomColl;

newFtr.Shape = geom2;

newFtr.Store();

}

}

Best regards,

Mikael

[BrentHoskisson · Accepted solution]

It is mostly there, you just need to do geomColl.AddGeometry on all of the interior rings of your original polygon.  I am fairly certain that any interior rings not in your exterior ring will be ignored.  However, if not, you might have to run an intersect first to see.

Good Luck

Brent 

[Mikael-J]

Hi Brent!

You are so right. It's worked like a charm to add the interior rings as well.

Many thanks!

/Mikael