public static Polygon CreatePolygon( 
   IEnumerable<Segment> segments,
   SpatialReference spatialReference
)

List<Segment> segmentList = new List<Segment>(30);
ICollection<Segment> collection = segmentList;
polygon.GetAllSegments(ref collection);
// segmentList.Count = 4
// segmentList.Capacity = 30

// use the segments to build another polygon
Polygon polygonFromSegments = PolygonBuilderEx.CreatePolygon(collection);

/// <summary>
/// This method takes an input multi part geometry and breaks the parts into individual standalone geometries.
/// This method must be called on the MCT. Use QueuedTask.Run.
/// </summary>
/// <param name="inputGeometry">The geometry to be exploded into the individual parts.</param>
/// <returns>An enumeration of individual parts as standalone geometries. The type of geometry is maintained, i.e.
/// if the input geometry is of type Polyline then each geometry in the return is of type Polyline as well.
/// If the input geometry is of type Unknown then an empty list is returned.</returns>
/// <remarks>This method must be called on the MCT. Use QueuedTask.Run.</remarks>
public IEnumerable<Geometry> MultipartToSinglePart(Geometry inputGeometry)
{
  // list holding the part(s) of the input geometry
  List<Geometry> singleParts = new List<Geometry>();

  // check if the input is a null pointer or if the geometry is empty
  if (inputGeometry == null || inputGeometry.IsEmpty)
    return singleParts;

  // based on the type of geometry, take the parts/points and add them individually into a list
  switch (inputGeometry.GeometryType)
  {
    case GeometryType.Envelope:
      singleParts.Add(inputGeometry.Clone() as Envelope);
      break;
    case GeometryType.Multipatch:
      singleParts.Add(inputGeometry.Clone() as Multipatch);
      break;
    case GeometryType.Multipoint:
      var multiPoint = inputGeometry as Multipoint;

      foreach (var point in multiPoint.Points)
      {
        // add each point of collection as a standalone point into the list
        singleParts.Add(point);
      }
      break;
    case GeometryType.Point:
      singleParts.Add(inputGeometry.Clone() as MapPoint);
      break;
    case GeometryType.Polygon:
      var polygon = inputGeometry as Polygon;

      foreach (var polygonPart in polygon.Parts)
      {
        // use the PolygonBuilderEx turning the segments into a standalone 
        // polygon instance
        singleParts.Add(PolygonBuilderEx.CreatePolygon(polygonPart));
      }
      break;
    case GeometryType.Polyline:
      var polyline = inputGeometry as Polyline;

      foreach (var polylinePart in polyline.Parts)
      {
        // use the PolylineBuilderEx turning the segments into a standalone
        // polyline instance
        singleParts.Add(PolylineBuilderEx.CreatePolyline(polylinePart));
      }
      break;
    case GeometryType.Unknown:
      break;
    default:
      break;
  }

  return singleParts;
}

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

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build geometry
  List<Coordinate2D> plyCoords = new List<Coordinate2D>();
  plyCoords.Add(new Coordinate2D(1, 7));
  plyCoords.Add(new Coordinate2D(2, 7));
  plyCoords.Add(new Coordinate2D(2, 6.7));
  plyCoords.Add(new Coordinate2D(3, 6.7));
  plyCoords.Add(new Coordinate2D(3, 6.1));
  plyCoords.Add(new Coordinate2D(1, 6.1));
  //At 2.x - Polygon poly = PolygonBuilder.CreatePolygon(plyCoords);
  Polygon poly = PolygonBuilderEx.CreatePolygon(plyCoords);

  //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, poly, polySym);
  //         polyElm.SetName("New Polygon"); 
  GraphicElement polyElm = ElementFactory.Instance.CreateGraphicElement(layout, poly, polySym, "New Polygon");
});

//Create a graphic lasso element with simple line and fill styles.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build geometry
  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));
  //At 2.x - Polygon poly = PolygonBuilder.CreatePolygon(plyCoords);
  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);
  //At 2.x - GraphicElement polyElm = LayoutElementFactory.Instance.CreatePolygonGraphicElement(layout, poly, polySym);
  //         polyElm.SetName("New Lasso"); 
  GraphicElement polyElm = ElementFactory.Instance.CreateGraphicElement(layout, poly, polySym, "New Lasso");
});

//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");

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

//Build geometry
List<Coordinate2D> plyCoords = new List<Coordinate2D>();
plyCoords.Add(new Coordinate2D(1, 7));
plyCoords.Add(new Coordinate2D(2, 7));
plyCoords.Add(new Coordinate2D(2, 6.7));
plyCoords.Add(new Coordinate2D(3, 6.7));
plyCoords.Add(new Coordinate2D(3, 6.1));
plyCoords.Add(new Coordinate2D(1, 6.1));
Polygon poly = PolygonBuilderEx.CreatePolygon(plyCoords);

//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);

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