The boundary of this geometry. A polygon's boundary is a polyline. A polyline's boundary is a multipoint. A point or multipoint's boundary is an empty point or multipoint.

[Visual Basic .NET]
**Public ReadOnly Property Boundary As **IGeometry

[C#]
**public **IGeometry **Boundary {get;}**

[C++]
**HRESULT get_Boundary(**
**IGeometry**** outBoundary
**);**

[C++]
**Parameters**
*outBoundary* [out, retval]

* outBoundary* is a parameter of type **IGeometry****

#### Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

#### Description

The Boundary of a Geometry is the part one the exterior of the Geometry. The Boundary is one Dimension lower than the Dimension of the original Geometry. The Boundary of a Polygon are the Polylines that form the Rings of the Polygon. The Boundary of a Polyline is a Multipoint corresponding to the endpoints of each Path in the Polyline. The Boundary of a Multipoint is an empty set.

#### Remarks

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.

[C#]
//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

#### See Also

ITopologicalOperator Interface
#### .NET Samples

ViperPin tool