public static Polyline CreatePolyline( 
   SpatialReference spatialReference
)

{
  polyline = PolylineBuilderEx.CreatePolyline(bezierSegment);
}

{
  //Note: Must be on QueuedTask.Run
  //Build geometry
  Coordinate2D pt1 = new Coordinate2D(1, 7.5);
  Coordinate2D pt2 = new Coordinate2D(1.66, 8);
  Coordinate2D pt3 = new Coordinate2D(2.33, 7.1);
  Coordinate2D pt4 = new Coordinate2D(3, 7.5);
  var bez = new CubicBezierBuilderEx(pt1, pt2, pt3, pt4);
  var bezSeg = bez.ToSegment();
  Polyline bezPl = PolylineBuilderEx.CreatePolyline(bezSeg, AttributeFlags.AllAttributes);

  //Set symbology, create and add element to layout
  CIMLineSymbol lineSym = SymbolFactory.Instance.ConstructLineSymbol(
    ColorFactory.Instance.RedRGB, 4.0, SimpleLineStyle.DashDot);

  ElementFactory.Instance.CreateGraphicElement(layout, bezPl, lineSym, "New Bezier");
}

{
  //Note: Must be on QueuedTask.Run
  //Build geometry
  List<Coordinate2D> plCoords = new List<Coordinate2D>();
  plCoords.Add(new Coordinate2D(1.5, 10.5));
  plCoords.Add(new Coordinate2D(1.25, 9.5));
  plCoords.Add(new Coordinate2D(1, 10.5));
  plCoords.Add(new Coordinate2D(0.75, 9.5));
  plCoords.Add(new Coordinate2D(0.5, 10.5));
  plCoords.Add(new Coordinate2D(0.5, 1));
  plCoords.Add(new Coordinate2D(0.75, 2));
  plCoords.Add(new Coordinate2D(1, 1));
  Polyline linePl = PolylineBuilderEx.CreatePolyline(plCoords);

  //Set symbology, create and add element to layout
  CIMLineSymbol lineSym = SymbolFactory.Instance.ConstructLineSymbol(
            ColorFactory.Instance.BlackRGB, 2.0, SimpleLineStyle.Solid);
  //var graphic = GraphicFactory.Instance.CreateShapeGraphic(linePl, lineSym);

  var ge = ElementFactory.Instance.CreateGraphicElement(
                          layout, linePl, lineSym, "New Freehand");
}

{
  //Note: Must be on QueuedTask.Run

  //Build geometry
  List<Coordinate2D> plCoords = new List<Coordinate2D>();
  plCoords.Add(new Coordinate2D(1, 8.5));
  plCoords.Add(new Coordinate2D(1.66, 9));
  plCoords.Add(new Coordinate2D(2.33, 8.1));
  plCoords.Add(new Coordinate2D(3, 8.5));
  Polyline linePl = PolylineBuilderEx.CreatePolyline(plCoords);

  //Reference a line symbol in a style
  var ProjectStyles = Project.Current.GetItems<StyleProjectItem>();
  StyleProjectItem style = ProjectStyles.First(x => x.Name == "ArcGIS 2D");
  var symStyle = style.SearchSymbols(StyleItemType.LineSymbol, "Line with 2 Markers")[0];
  CIMLineSymbol lineSym = symStyle.Symbol as CIMLineSymbol;
  lineSym.SetSize(20);

  //Set symbology, create and add element to layout
  //CIMLineSymbol lineSym = SymbolFactory.Instance.ConstructLineSymbol(ColorFactory.Instance.BlueRGB, 4.0, SimpleLineStyle.Solid);
  ElementFactory.Instance.CreateGraphicElement(
    layout, linePl, lineSym, "New Line");
}