public EllipticArcBuilderEx( 
   Coordinate2D centerPt,
   double radius,
   ArcOrientation orientation,
   SpatialReference spatialReference
)

{
  // Construct a circle with center at (-1,-1), radius = 2, and oriented clockwise.
  // Use a builderEx convenience method or use a builderEx constructor.

  Coordinate2D centerPtCoord = new Coordinate2D(-1, -1);

  // Builder convenience methods don't need to run on the MCT.
  EllipticArcSegment circle = EllipticArcBuilderEx.CreateCircle(centerPtCoord, 2, ArcOrientation.ArcClockwise);
  // circle.IsCircular = true
  // circle.IsCounterClockwise = false
  // circle.IsMinor = false

  double startAngle, rotationAngle, centralAngle, semiMajor, semiMinor;
  Coordinate2D actualCenterPt;
  circle.QueryCoords(out actualCenterPt, out startAngle, out centralAngle, out rotationAngle, out semiMajor, out semiMinor);

  // semiMajor = 2.0
  // semiMinor = 2.0
  // startAngle = PI/2
  // centralAngle = -2*PI
  // rotationAngle = 0
  // endAngle = PI/2

  // This EllipticArcBuilderEx constructor doesn't need to run on the MCT.
  EllipticArcBuilderEx builder = new EllipticArcBuilderEx(centerPtCoord, 2, ArcOrientation.ArcClockwise);
  EllipticArcSegment otherCircle = builder.ToSegment();
}

{
  //Note: Must be on QueuedTask.Run(() => { ...
  //Build geometry
  Coordinate2D center = new Coordinate2D(4.5, 4);
  var eabCir = new EllipticArcBuilderEx(center, 0.5, ArcOrientation.ArcClockwise);
  var cir = eabCir.ToSegment();

  var poly = PolygonBuilderEx.CreatePolygon(
    PolylineBuilderEx.CreatePolyline(cir, AttributeFlags.AllAttributes));

  //Set symbology, create and add element to layout
  CIMTextSymbol sym = SymbolFactory.Instance.ConstructTextSymbol(
                  ColorFactory.Instance.GreenRGB, 10, "Arial", "Regular");
  string text = "Circle, circle, circle";

  GraphicElement cirTxtElm = ElementFactory.Instance.CreateTextGraphicElement(
    layout, TextType.CircleParagraph, poly, sym, text, "New Circle Text", false);
}

{
  //Note: Must be on QueuedTask.Run

  //Build geometry
  Coordinate2D center = new Coordinate2D(4.5, 2.75);
  var eabElp = new EllipticArcBuilderEx(center, 0, 1, 0.45, ArcOrientation.ArcClockwise);
  var ellipse = eabElp.ToSegment();

  var poly = PolygonBuilderEx.CreatePolygon(
    PolylineBuilderEx.CreatePolyline(ellipse, AttributeFlags.AllAttributes));

  //Set symbology, create and add element to layout
  CIMTextSymbol sym = SymbolFactory.Instance.ConstructTextSymbol(
                        ColorFactory.Instance.BlueRGB, 10, "Arial", "Regular");
  string text = "Ellipse, ellipse, ellipse";

  GraphicElement ge = ElementFactory.Instance.CreateTextGraphicElement(
    layout, TextType.PolygonParagraph, poly, sym, text, "New Ellipse Text", false);
}

{
  //Note: Must be on QueuedTask.Run

  //Build geometry
  Coordinate2D center = new Coordinate2D(2, 2.75);
  var eabElp = new EllipticArcBuilderEx(
                           center, 0, 1, 0.45, ArcOrientation.ArcClockwise);
  var ellipse = eabElp.ToSegment();

  //Set symbology, create and add element to layout
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
                        ColorFactory.Instance.GreenRGB, 2.0, SimpleLineStyle.Dot);
  CIMPolygonSymbol ellipseSym = SymbolFactory.Instance.ConstructPolygonSymbol(
                   ColorFactory.Instance.GreyRGB, SimpleFillStyle.Vertical, outline);

  var poly = PolygonBuilderEx.CreatePolygon(
    PolylineBuilderEx.CreatePolyline(ellipse, AttributeFlags.AllAttributes));

  var ge = ElementFactory.Instance.CreatePredefinedShapeGraphicElement(
    layout, PredefinedShape.Ellipse, poly.Extent.Center, 0, 0, ellipseSym,
    "New Ellipse2", false, new ElementInfo() { Anchor = Anchor.TopRightCorner });
}