The boundary of a polyline is the set of start and end points of each path, the interior is the set of points in the polyline that are not in the boundary, and the exterior is the set of points that are not in the boundary or the interior.
A Polyline is based upon the parent Geometry class. The Geometry class is immutable which means that you can not change its shape once it is created. If you need to modify a Polyline once it has been created, use the PolylineBuilder class instead. The PolylineBuilder.ToGeometry method will provide you with the Polyline object.
System.Object
ArcGIS.Core.Geometry.Geometry
ArcGIS.Core.Geometry.Multipart
ArcGIS.Core.Geometry.Polyline
Target Platforms: Windows 10, Windows 8.1, Windows 7