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ITopologicalOperator.Boundary Property (ArcObjects .NET 10.8 SDK)
 ArcObjects Help for .NET developers > ArcObjects Help for .NET developers > ArcObjects namespaces > Geometry > ESRI.ArcGIS.Geometry > Interfaces > IT > ITopologicalOperator Interface > ITopologicalOperator.Boundary Property
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# ITopologicalOperator.Boundary Property

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