IGeometryCollection of Polylines returns Paths - arcobjects

Question

I have an file of points which are to be converted to a set of polylines. Some of the lines are multipart and I want to convert them to singlepart.
The points are processed and the polylines added to an Interim featureclass (for backup purposes). If a line is multipart it is added to this interim featureclass as multipart.
The interim featureclass is then read and it's features copied to a base featureclass. This works fine for single part features but I keep getting the 'No support for this geometry type' error when converting the multiparts to singleparts. The problem is that to create the multipart feature from a set of points I have to use a segment collection as a Path. I've tried setting this to a polyline but then adding line segments to it causes an error (wrong geometry type).
When I add the multipart features to the interim featureclass the geometries are Polylines. When I retrieve them later (by putting thte shape into a new GeometryCollection) the geometry collection is a Polyline but the individual geometries are Paths (?).
The code is:
1. Add points to interim featureclass by putting them in a pointcollection.
pPtColl = (IPointCollection4)new Polyline();
pGeomColl = (IGeometryCollection)new Polyline();
// Fill point collection
.......
// Create a path made up of segments from the point collection
ISegment pSegment;
ISegmentCollection pSegColl = (ISegmentCollection)new ESRI.ArcGIS.Geometry.Path(); // Fails if changed to new Polyline()
// M and Z aware
if (bHasZ == true)
{
pZAware = (IZAware)pSegColl;
pZAware.ZAware = true;
}
if (bHasM == true)
{
pMAware = (IMAware)pSegColl;
pMAware.MAware = true;
}
for (int n = 1; n < pPtColl.PointCount; n++)
{
pSegment = (ISegment)new Line();
pSegment.SpatialReference = pSpRef;
pSegment.FromPoint = pPtColl.Point[n - 1];
pSegment.ToPoint = pPtColl.Point[n];
pSegColl.AddSegment(pSegment, oMissing, oMissing);
}
pGeomColl.AddGeometry(pSegColl as IGeometry, oMissing, oMissing);
pGeom = (IGeometry)pGeomColl; // pGeom has geometry type = Polyline
pGeom.SpatialReference = pSpRef;
pFeat.Shape = pGeom;
This part of the code all works fine.
When processing these features from the interim featureclass to add them to the base featureclass I get an error because the geometry type from the geometry collection is 'Path' not 'Polyline'.
// Read the geometry from the interim feature into a geometry collection
pGeomColl = (IGeometryCollection)new Polyline();
pGeomColl = (IGeometryCollection)pFromFeature.ShapeCopy;
for (int j = 0; j < pGeomColl.GeometryCount; j++)
{
// Create a new (Polyline) feature pToFeat and populate its attributes
pToFeat = pToFC.CreateFeature();
....
// pGeomColl has geometry type = Polyline
pGeom = pGeomColl.Geometry[j]; // pGeom has geometry type = Path
pToFeat.Shape = pGeom; // Fails. pToFeat is a Polyline.
}
How can I ensure that the geometry collection contains geometries with Polylines rather than Paths?
Thanks,
JM

Answer 1

I have found what I condsider to be a workaround for this problem but it's not very pretty.
The solution is to cast the Path geometry into a polyline and then cast it back into a geometry when assigning it to the .Shape attribute.
if (pToFeat .ShapeCopy.GeometryType == esriGeometryType.esriGeometryPolyline && pGeom.GeometryType == esriGeometryType.esriGeometryPath)
{
IPolyline pPoly = (IPolyline)new Polyline();
pPoly = geometryToPolyline(pGeom, bHasZ, bHasM, ref sError);
if (sError.Length > 0)
{
sError = "processAdds; ID = " + sID + " OID = " + iOID.ToString() + sNL + sError;
clsMain.write_log(sError, clsMain.m_eLogType.FATAL);
iErrorCount++;
}
else
{
pToFeat.Shape = (IGeometry)pPoly;
}
}
private static IPolyline geometryToPolyline(IGeometry pInputGeom, bool bHasZ, bool bHasM, ref string sError)
{
IPolyline pPoly = null;
IGeometryCollection pPolyColl = null;
IZAware pZAware;
IMAware pMAware;
double dZ;
ISpatialReference pSpRef;
bool bIsMulti;
esriGeometryType pType;
try
{
sError = "";
pSpRef = pInputGeom.SpatialReference;
// Create a new polyline
pPoly = (IPolyline)new Polyline();
if (bHasZ == true)
{
pZAware = (IZAware)pPoly;
pZAware.ZAware = true;
}
if (bHasM == true)
{
pMAware = (IMAware)pPoly;
pMAware.MAware = true;
}
// Create the geometry collection
pPolyColl = (IGeometryCollection)new Polyline();
if (bHasZ == true)
{
pZAware = (IZAware)pPolyColl;
pZAware.ZAware = true;
}
if (bHasM == true)
{
pMAware = (IMAware)pPolyColl;
pMAware.MAware = true;
}
// Set the polyline as the geometry collection
pPoly = (IPolyline)pPolyColl;
pPoly.SpatialReference = pSpRef;
pPolyColl.AddGeometry(pInputGeom);
return pPoly;
}
catch (Exception ex)
{
System.Diagnostics.StackTrace pStack = new System.Diagnostics.StackTrace(ex, true);
System.Diagnostics.StackFrame pFrame = pStack.GetFrame(pStack.FrameCount - 1);
int iLineNo = pFrame.GetFileLineNumber();
sError = "ERROR: geometryToPolyline; Line: " + iLineNo + "\n" + ex.ToString();
return pPoly;
}
}