public static LineSegment CreateLineSegment( 
   LineSegment segment,
   SpatialReference spatialReference
)

{
  // Use a builderEx convenience method or use a builderEx constructor.

  MapPoint startPt = MapPointBuilderEx.CreateMapPoint(1.0, 1.0);
  MapPoint endPt = MapPointBuilderEx.CreateMapPoint(2.0, 1.0);

  // BuilderEx convenience methods don't need to run on the MCT.
  LineSegment lineFromMapPoint = LineBuilderEx.CreateLineSegment(startPt, endPt);

  // coordinate2D
  Coordinate2D start2d = (Coordinate2D)startPt;
  Coordinate2D end2d = (Coordinate2D)endPt;

  LineSegment lineFromCoordinate2D = LineBuilderEx.CreateLineSegment(start2d, end2d);

  // coordinate3D
  Coordinate3D start3d = (Coordinate3D)startPt;
  Coordinate3D end3d = (Coordinate3D)endPt;

  LineSegment lineFromCoordinate3D = LineBuilderEx.CreateLineSegment(start3d, end3d);

  // lineSegment
  LineSegment anotherLineFromLineSegment = LineBuilderEx.CreateLineSegment(lineFromCoordinate3D);


  // builderEx constructors don't need to run on the MCT
  LineBuilderEx lbEx = new LineBuilderEx(startPt, endPt);
  lineFromMapPoint = lbEx.ToSegment() as LineSegment;

  lbEx = new LineBuilderEx(start2d, end2d);
  lineFromCoordinate2D = lbEx.ToSegment() as LineSegment;

  lbEx = new LineBuilderEx(start3d, end3d);
  lineFromCoordinate3D = lbEx.ToSegment() as LineSegment;

  lbEx = new LineBuilderEx(startPt, endPt);
  lineFromMapPoint = lbEx.ToSegment() as LineSegment;

  lbEx = new LineBuilderEx(lineFromCoordinate3D);
  anotherLineFromLineSegment = lbEx.ToSegment() as LineSegment;
}