public CIMStroke ConstructStroke( 
   CIMColor color,
   double width
)

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 }
};