EDN: ESRI Developer Network
Defines this geometry to be the union of the inputs. More efficient for unioning multiple geometries than calling Union repeatedly.
[Visual Basic 6.0] Sub ConstructUnion(
ByVal geometries As IEnumGeometry _
)
[Visual Basic .NET] Public Sub ConstructUnion ( _ ByVal geometries As IEnumGeometry _ )
[C#] public void ConstructUnion ( IEnumGeometry geometries );
[Java] public void constructUnion ( IEnumGeometry geometries ) throws IOException, AutomationException
[C++] HRESULT ConstructUnion( IEnumGeometry* geometries );
ConstructUnion simultaneously Unions an Enumeration of geometries of the same Dimension into a single geometry. ConstructUnion is more efficient for unioning a large collection of geometries simultaneously rather than cycling through each geometry individually.
ITopologicalOperator methods must be applied on high-level geometries only. High-Level geometries are point, multipoint, polyline and polygon. To use this method with low-level geometries such as segments (Line, Circular Arc, Elliptic Arc, Bézier Curve), paths or rings, they must be wrapped into high-level geometries types.
This method does not support GeometryBags.
//The following code shows to wrap a line segment into a polyline in C#
//Assume a line (line1 as ILine) is already created
object obj = Type.Missing;
ISegmentCollection segCollection = new PolylineClass() as ISegmentCollection;
segCollection.AddSegment((ISegment)line1, ref obj, ref obj);
//Set the spatial reference on the new polyline
//The spatial reference is not transfered automatically from the segments
IGeometry geom = segCollection as IGeometry;
geom.SpatialReference = spatialRef;
//Can now be used with ITopologicalOperator methods
'How to wrap a line segment into a polyline in VB6
'Assume a line (pLine as ILine) is already created
dim psc as ISegmentCollection
set psc = New Polyline
psc.addsegment pline
'Set the spatial reference on the new polyline
'The spatial reference is not transfered automatically from the segments
dim pgeo as IGeometry
set pgeo = psc
set pgeo.SpatialReference = pMyspatialReference
'Can now be used with ITopologicalOperator methods
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