public class CIMPolygonSymbol : CIMMultiLayerSymbol, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

//Create a polygon graphic using an envelope with simple line and fill styles.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D envelope
  Coordinate2D env_ll = new Coordinate2D(1.0, 4.75);
  Coordinate2D env_ur = new Coordinate2D(3.0, 5.75);
  //At 2.x - Envelope env = EnvelopeBuilder.CreateEnvelope(env_ll, env_ur);
  Envelope env = EnvelopeBuilderEx.CreateEnvelope(env_ll, env_ur);

  //Set symbolology, create and add element to layout
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
    ColorFactory.Instance.BlueRGB, 2.0, SimpleLineStyle.DashDotDot);
  CIMPolygonSymbol polySym = SymbolFactory.Instance.ConstructPolygonSymbol(
    ColorFactory.Instance.RedRGB, SimpleFillStyle.ForwardDiagonal, outline);
  //At 2.x - GraphicElement polyElm =
  //            LayoutElementFactory.Instance.CreatePolygonGraphicElement(layout, env, polySym);
  //         polyElm.SetName("New Polygon");
  GraphicElement polyElm = ElementFactory.Instance.CreateGraphicElement(
    layout, env, polySym, "New Polygon");
});

//Create a circle graphic element using a simple line and fill styles.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build geometry
  Coordinate2D center = new Coordinate2D(2, 4);
  //At 2.x - EllipticArcBuilder eabCir = new EllipticArcBuilder(center, 0.5, esriArcOrientation.esriArcClockwise);
  var eabCir = new EllipticArcBuilderEx(center, 0.5, ArcOrientation.ArcClockwise);
  EllipticArcSegment cir = eabCir.ToSegment();

  //Set symbolology, create and add element to layout
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlackRGB, 2.0, SimpleLineStyle.Dash);
  CIMPolygonSymbol circleSym = SymbolFactory.Instance.ConstructPolygonSymbol(ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid, outline);
  //At 2.x - GraphicElement cirElm = LayoutElementFactory.Instance.CreateCircleGraphicElement(layout, cir, circleSym);
  //         cirElm.SetName("New Circle");

  var polyLine = PolylineBuilderEx.CreatePolyline(cir);
  GraphicElement cirElm = ElementFactory.Instance.CreateGraphicElement(layout, polyLine, circleSym, "New Circle");
});

//Create an ellipse graphic with simple line and fill styles.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build geometry
  Coordinate2D center = new Coordinate2D(2, 2.75);
  //At 2.x - EllipticArcBuilder eabElp = new EllipticArcBuilder(center, 0, 1, 0.45, esriArcOrientation.esriArcClockwise);
  var eabElp = new EllipticArcBuilderEx(center, 0, 1, 0.45, ArcOrientation.ArcClockwise);
  EllipticArcSegment ellipse = eabElp.ToSegment();

  //Set symbolology, 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);
  //At 2.x - GraphicElement elpElm = LayoutElementFactory.Instance.CreateEllipseGraphicElement(layout, ellipse, ellipseSym);
  //         elpElm.SetName("New Ellipse");

  var polyLine = PolylineBuilderEx.CreatePolyline(ellipse);
  GraphicElement elpElm = ElementFactory.Instance.CreateGraphicElement(layout, polyLine, ellipseSym, "New Ellipse");
});

//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 symbolology, 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 elpElm = ElementFactory.Instance.CreateGraphicElement(
  container, poly, ellipseSym, "New Ellipse");

//Must be on QueuedTask.Run(() => { ...

List<Coordinate2D> plyCoords = new List<Coordinate2D>();
plyCoords.Add(new Coordinate2D(1, 1));
plyCoords.Add(new Coordinate2D(1.25, 2));
plyCoords.Add(new Coordinate2D(1.5, 1.1));
plyCoords.Add(new Coordinate2D(1.75, 2));
plyCoords.Add(new Coordinate2D(2, 1.1));
plyCoords.Add(new Coordinate2D(2.25, 2));
plyCoords.Add(new Coordinate2D(2.5, 1.1));
plyCoords.Add(new Coordinate2D(2.75, 2));
plyCoords.Add(new Coordinate2D(3, 1));
Polygon poly = PolygonBuilderEx.CreatePolygon(plyCoords);

//Set symbolology, create and add element to layout
CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
            ColorFactory.Instance.BlackRGB, 2.0, SimpleLineStyle.Solid);
CIMPolygonSymbol polySym = SymbolFactory.Instance.ConstructPolygonSymbol(
         ColorFactory.Instance.RedRGB, SimpleFillStyle.ForwardDiagonal, outline);

ElementFactory.Instance.CreateGraphicElement(
  container, poly, polySym, "New Lasso");

//Create a simple 2D rectangle graphic and apply simple fill and
//outline symbols.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D envelope geometry
  Coordinate2D rec_ll = new Coordinate2D(1.0, 4.75);
  Coordinate2D rec_ur = new Coordinate2D(3.0, 5.75);
  //At 2.x - Envelope rec_env = EnvelopeBuilder.CreateEnvelope(rec_ll, rec_ur);
  Envelope rec_env = EnvelopeBuilderEx.CreateEnvelope(rec_ll, rec_ur);

  //Set symbolology, create and add element to layout
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
    ColorFactory.Instance.BlackRGB, 5.0, SimpleLineStyle.Solid);
  CIMPolygonSymbol polySym = SymbolFactory.Instance.ConstructPolygonSymbol(
    ColorFactory.Instance.GreenRGB, SimpleFillStyle.DiagonalCross, outline);

  //At 2.x - GraphicElement recElm =
  //           LayoutElementFactory.Instance.CreateRectangleGraphicElement(
  //                                                  layout, rec_env, polySym);
  //         recElm.SetName("New Rectangle");
  //
  GraphicElement recElm = ElementFactory.Instance.CreateGraphicElement(
    container, rec_env, polySym, "New Rectangle");
  //Or use Predefined shape
  GraphicElement recElm2 = ElementFactory.Instance.CreatePredefinedShapeGraphicElement(
                            container, PredefinedShape.Rectangle, rec_env, polySym, 
                            "New Rectangle2");
});

CIMPolygonSymbol polygonSymbol = SymbolFactory.Instance.ConstructPolygonSymbol(ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid);

CIMStroke outline = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlueRGB, 2.0, SimpleLineStyle.Solid);
CIMPolygonSymbol fillWithOutline = SymbolFactory.Instance.ConstructPolygonSymbol(ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid, outline);

CIMPolygonSymbol fillWithoutOutline = SymbolFactory.Instance.ConstructPolygonSymbol(ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid, null);

/// <summary>
/// Create a polygon symbol using the ConstructHatchFill method . <br/>
/// ![PolygonSymbolDiagonalCrossHatch](http://Esri.github.io/arcgis-pro-sdk/images/Symbology/ConstructHatchFill.png)
/// </summary>
/// <returns></returns>
private static Task<CIMPolygonSymbol> CreateHatchFillPolygonAsync()
{
  return QueuedTask.Run<CIMPolygonSymbol>(() =>
  {
    CIMStroke lineStroke = SymbolFactory.Instance.ConstructStroke(CIMColor.CreateRGBColor(51, 51, 51, 60), 4, SimpleLineStyle.Solid);
    //gradient
    var hatchFill = SymbolFactory.Instance.ConstructHatchFill(lineStroke, 45, 6, 0);

    List<CIMSymbolLayer> symbolLayers = new List<CIMSymbolLayer>
    {
      hatchFill
    };
    return new CIMPolygonSymbol() { SymbolLayers = symbolLayers.ToArray() };
  });
}