Union(IEnumerable<Geometry>) Method

In This Topic

Constructs the set-theoretic union of the input geometries.

Syntax

C#
Visual Basic (Declaration)

Geometry Union( 
   IEnumerable<Geometry> geometries
)

Overloads Function Union( _
   ByVal geometries As IEnumerable(Of Geometry) _
) As Geometry

Parameters

geometries: The collection of geometries to union. If a geometry is an Envelope, it is converted to a Polygon.

Return Value

A geometry representing the union of the input geometries.

Exceptions

Exception	Description
System.ArgumentNullException	Geometries is null or empty.
System.NotImplementedException	The method is not implemented for GeometryBag.
System.ArgumentException	Geometry is the wrong type for this operation. Cannot union geometries that have unequal dimensions. GeometryDimensionType
System.InvalidOperationException	Incompatible spatial references between the input geometries.
System.NotImplementedException	One of the geometries has a spatial reference which is an image coordinate system.

Remarks

An exception is thrown if the SpatialReferences of the geometries are not equal or if the dimension of the geometries are not equal. This means that points and multipoints are considered to be the same type, and polygons and envelopes are considered to be the same type.

GeometryEngine Union

Example

Union many Polylines

// union many polylines

List<Coordinate2D> coords = new List<Coordinate2D>()
{
  new Coordinate2D(1, 2), new Coordinate2D(3, 4), new Coordinate2D(4, 2),
  new Coordinate2D(5, 6), new Coordinate2D(7, 8), new Coordinate2D(8, 4),
  new Coordinate2D(9, 10), new Coordinate2D(11, 12), new Coordinate2D(12, 8),
  new Coordinate2D(10, 8), new Coordinate2D(12, 12), new Coordinate2D(14, 10)
};

// create Disjoint lines
List<Polyline> manyLines = new List<Polyline>
{
  PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[0], coords[1], coords[2]}, SpatialReferences.WGS84),
  PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[3], coords[4], coords[5]}),
  PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[6], coords[7], coords[8]})
};

Polyline polyline = GeometryEngine.Instance.Union(manyLines) as Polyline;

Union many Polygons

// union many polygons

List<Coordinate3D> coordsZ = new List<Coordinate3D>()
{
  new Coordinate3D(1, 2, 0), new Coordinate3D(3, 4, 1), new Coordinate3D(4, 2, 2),
  new Coordinate3D(5, 6, 3), new Coordinate3D(7, 8, 4), new Coordinate3D(8, 4, 5),
  new Coordinate3D(9, 10, 6), new Coordinate3D(11, 12, 7), new Coordinate3D(12, 8, 8),
  new Coordinate3D(10, 8, 9), new Coordinate3D(12, 12, 10), new Coordinate3D(14, 10, 11)
};

// create polygons
List<Polygon> manyPolygonsZ = new List<Polygon>
{
  PolygonBuilderEx.CreatePolygon(new List<Coordinate3D>(){coordsZ[0], coordsZ[1], coordsZ[2]}, SpatialReferences.WGS84),
  PolygonBuilderEx.CreatePolygon(new List<Coordinate3D>(){coordsZ[3], coordsZ[4], coordsZ[5]}),
  PolygonBuilderEx.CreatePolygon(new List<Coordinate3D>(){coordsZ[6], coordsZ[7], coordsZ[8]})
};

Polygon polygon = GeometryEngine.Instance.Union(manyPolygonsZ) as Polygon;

Requirements

Target Platforms: Windows 11, Windows 10

ArcGIS Pro version: 3 or higher.

Reference

IGeometryEngine Interface
IGeometryEngine Members
Overload List

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