Buffer(IEnumerable<Geometry>,Double) Method

In This Topic

Creates buffers at the specified distance around the given geometries. Will union the results of all buffers.

Syntax

C#
Visual Basic (Declaration)

public Geometry Buffer( 
   IEnumerable<Geometry> geometries,
   double distance
)

Public Overloads Function Buffer( _
   ByVal geometries As IEnumerable(Of Geometry), _
   ByVal distance As Double _
) As Geometry

Parameters

geometries: Specifies the input geometries.
distance: The distance (in the unit of the geometry's spatial reference) to buffer the geometries.

Return Value

The polygon that represents the buffered area.

Exceptions

Exception	Description
System.ArgumentNullException	Geometries is null or empty.
System.NotImplementedException	The method is not implemented for GeometryBag.
System.ArgumentException	The buffer distance must be a valid floating point number.

Remarks

The returned polygon is the union of all the buffered geometries.

If the buffer distance is zero and the input geometry is a polygon or an envelope, then a polygon is created from the input geometries.

If the distance is less than or equal to zero and the input geometry is not a polygon or an envelope, then an empty polygon is created.

The spatial reference of the output geometries is the first not null or unknown spatial reference found in the list of geometries. All other geometries are projected to this spatial reference, if necessary. If no such spatial reference is found, then the unknown spatial reference is used if it is found in the list. Otherwise, the spatial reference is null.

Example

Zoom to a specified point

//Create a point
var pt = MapPointBuilderEx.CreateMapPoint(x, y, 
               SpatialReferenceBuilder.CreateSpatialReference(4326));
//Buffer it - for purpose of zoom
var poly = GeometryEngine.Instance.Buffer(pt, buffer_size);

//do we need to project the buffer polygon?
if (!MapView.Active.Map.SpatialReference.IsEqual(poly.SpatialReference))
{
  //project the polygon
  poly = GeometryEngine.Instance.Project(poly, MapView.Active.Map.SpatialReference);
}

// Must run on MCT.
QueuedTask.Run(() =>
{
  //Zoom - add in a delay for animation effect
  MapView.Active.ZoomTo(poly, new TimeSpan(0, 0, 0, 3));
});

Buffer multiple MapPoints

// creates a buffer around each MapPoint

List<MapPoint> pts = new List<MapPoint>();
pts.Add(MapPointBuilderEx.CreateMapPoint(1.0, 1.0));
pts.Add(MapPointBuilderEx.CreateMapPoint(1.0, 2.0));
pts.Add(MapPointBuilderEx.CreateMapPoint(2.0, 2.0));
pts.Add(MapPointBuilderEx.CreateMapPoint(2.0, 1.0));

Geometry ptsBuffer = GeometryEngine.Instance.Buffer(pts, 0.25);
Polygon bufferResult = ptsBuffer as Polygon;      // bufferResult will have 4 parts

Buffer many different Geometry Types

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)
};

List<Geometry> manyGeometries = new List<Geometry>
{
    MapPointBuilderEx.CreateMapPoint(coords[9]),
    PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[0], coords[1], coords[2]}, SpatialReferences.WGS84),
    PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[3], coords[4], coords[5]}),
    PolygonBuilderEx.CreatePolygon(new List<Coordinate2D>(){coords[6], coords[7], coords[8]})
};

Geometry manyGeomBuffer = GeometryEngine.Instance.Buffer(manyGeometries, 0.25);

Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

Reference

GeometryEngine Class
GeometryEngine Members
Overload List

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