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

//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 symbolology, 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(
                        container, linePl, lineSym, "New Freehand");

//Create a simple 2D line graphic and apply an existing line
//style item as the symbology.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2d line 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));
  //At 2.x - Polyline linePl = PolylineBuilder.CreatePolyline(plCoords);
  Polyline linePl = PolylineBuilderEx.CreatePolyline(plCoords);

  //(optionally) Reference a line symbol in a style
  StyleProjectItem lnStylePrjItm = Project.Current.GetItems<StyleProjectItem>()
                                .FirstOrDefault(item => item.Name == "ArcGIS 2D");
  SymbolStyleItem lnSymStyleItm = lnStylePrjItm.SearchSymbols(
                                StyleItemType.LineSymbol, "Line with 2 Markers")[0];
  CIMLineSymbol lineSym = lnSymStyleItm.Symbol as CIMLineSymbol;
  lineSym.SetSize(20);

  //Set symbolology, create and add element to layout

  //An alternative simple symbol is also commented out below.
  //This would elminate the four optional lines of code above that
  //reference a style.
  //
  //CIMLineSymbol lineSym = SymbolFactory.Instance.ConstructLineSymbol(
  //         ColorFactory.Instance.BlueRGB, 4.0, SimpleLineStyle.Solid);  
  //At 2.x - GraphicElement lineElm =
  //        LayoutElementFactory.Instance.CreateLineGraphicElement(
  //                                            layout, linePl, lineSym);

  GraphicElement lineElm = ElementFactory.Instance.CreateGraphicElement(
                                              container, linePl, lineSym);
  lineElm.SetName("New Line");
});

CIMLineSymbol lineSymbol = SymbolFactory.Instance.ConstructLineSymbol(ColorFactory.Instance.BlueRGB, 4.0, SimpleLineStyle.Solid);

CIMStroke stroke = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlackRGB, 2.0);
CIMLineSymbol lineSymbolFromStroke = SymbolFactory.Instance.ConstructLineSymbol(stroke);

//These methods must be called within the lambda passed to QueuedTask.Run
var lineStrokeRed = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.RedRGB, 4.0);
var markerCircle = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.RedRGB, 12, SimpleMarkerStyle.Circle);
markerCircle.MarkerPlacement = new CIMMarkerPlacementOnVertices()
{
  AngleToLine = true,
  PlaceOnEndPoints = true,
  Offset = 0
};
var lineSymbolWithCircles = new CIMLineSymbol()
{
  SymbolLayers = new CIMSymbolLayer[2] { markerCircle, lineStrokeRed }
};

//These methods must be called within the lambda passed to QueuedTask.Run
var lineStrokeRed = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.RedRGB, 4.0);
var markerCircle = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.RedRGB, 12, SimpleMarkerStyle.Circle);
markerCircle.MarkerPlacement = new CIMMarkerPlacementOnVertices()
{
  AngleToLine = true,
  PlaceOnEndPoints = true,
  Offset = 0
};
var lineSymbolWithCircles = new CIMLineSymbol()
{
  SymbolLayers = new CIMSymbolLayer[2] { markerCircle, lineStrokeRed }
};

//These methods must be called within the lambda passed to QueuedTask.Run
var markerTriangle = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.RedRGB, 12, SimpleMarkerStyle.Triangle);
markerTriangle.Rotation = -90; // or -90
markerTriangle.MarkerPlacement = new CIMMarkerPlacementOnLine() { AngleToLine = true, RelativeTo = PlacementOnLineRelativeTo.LineEnd };

var lineSymbolWithArrow = new CIMLineSymbol()
{
  SymbolLayers = new CIMSymbolLayer[2] { markerTriangle,
              SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.RedRGB, 2)
          }
};

//These methods must be called within the lambda passed to QueuedTask.Run
var markerTriangle = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.RedRGB, 12, SimpleMarkerStyle.Triangle);
markerTriangle.Rotation = -90; // or -90
markerTriangle.MarkerPlacement = new CIMMarkerPlacementOnLine() { AngleToLine = true, RelativeTo = PlacementOnLineRelativeTo.LineEnd };

var lineSymbolWithArrow = new CIMLineSymbol()
{
  SymbolLayers = new CIMSymbolLayer[2] { markerTriangle,
              SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.RedRGB, 2)
          }
};