ArcGIS Pro 2.7 API Reference Guide
ExteriorRingCount Property
Example 

ArcGIS.Core.Geometry Namespace > Polygon Class : ExteriorRingCount Property
Gets the number of exterior rings in this polygon.
Syntax
public int ExteriorRingCount {get;}
Public ReadOnly Property ExteriorRingCount As Integer
Remarks
An exterior ring is a part that is oriented clockwise.
Example
public void GetExteriorRings(Polygon inputPolygon)
{
  if (inputPolygon == null || inputPolygon.IsEmpty)
    return;

  // polygon part count
  int partCount = inputPolygon.PartCount;
  // polygon exterior ring count
  int numExtRings = inputPolygon.ExteriorRingCount;
  // get set of exterior rings for the polygon
  IList<Polygon> extRings = inputPolygon.GetExteriorRings();

  // test each part for "exterior ring"
  for (int idx = 0; idx < partCount; idx++)
  {
    bool isExteriorRing = inputPolygon.IsExteriorRing(idx);
  }
}
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

Polygon Class
Polygon Members