public class CIMGeometricEffectOffset : CIMGeometricEffect, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

/// <summary>
/// Create a line symbol with a dash and two markers.<br/>          
/// </summary>
/// <remarks>
/// This line symbol comprises three symbol layers listed below: 
/// 1. A solid stroke that has dashes.
/// 1. A circle marker.
/// 1. A square marker.
/// ![LineSymbolTwoMarkers](http://Esri.github.io/arcgis-pro-sdk/images/Symbology/line-dash-two-markers.png)
/// </remarks>
/// <returns></returns>
internal static Task<CIMLineSymbol> CreateLineDashTwoMarkersAync()
{
  return QueuedTask.Run<CIMLineSymbol>(() =>
  {

    var dash2MarkersLine = new CIMLineSymbol();

    var mySymbolLyrs = new CIMSymbolLayer[]
          {
                new CIMSolidStroke()
                {
                    Color = ColorFactory.Instance.BlackRGB,
                    Enable = true,
                    ColorLocked = true,
                    CapStyle = LineCapStyle.Round,
                    JoinStyle = LineJoinStyle.Round,
                    LineStyle3D = Simple3DLineStyle.Strip,
                    MiterLimit = 10,
                    Width = 1,
                    CloseCaps3D = false,
                    Effects = new CIMGeometricEffect[]
                    {
                        new CIMGeometricEffectDashes()
                        {
                            CustomEndingOffset = 0,
                            DashTemplate = new double[] {20, 10, 20, 10},
                            LineDashEnding = LineDashEnding.HalfPattern,
                            OffsetAlongLine = 0,
                            ControlPointEnding = LineDashEnding.NoConstraint
                        },
                        new CIMGeometricEffectOffset()
                        {
                            Method = GeometricEffectOffsetMethod.Bevelled,
                            Offset = 0,
                            Option = GeometricEffectOffsetOption.Fast
                        }
                    },
                },
                CreateCircleMarkerPerSpecs(),
                CreateSquareMarkerPerSpecs()
      };
    dash2MarkersLine.SymbolLayers = mySymbolLyrs;
    return dash2MarkersLine;
  });
}
private static CIMMarker CreateCircleMarkerPerSpecs()
{
  var circleMarker = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.BlackRGB, 5, SimpleMarkerStyle.Circle) as CIMVectorMarker;
  //Modifying the marker to align with line
  //First define "markerplacement"
  CIMMarkerPlacementAlongLineSameSize markerPlacement = new CIMMarkerPlacementAlongLineSameSize()
  {
    AngleToLine = true,
    Offset = 0,
    Endings = PlacementEndings.Custom,
    OffsetAlongLine = 15,
    PlacementTemplate = new double[] { 60 }
  };
  //assign the markerplacement to the marker
  circleMarker.MarkerPlacement = markerPlacement;
  return circleMarker;
}
private static CIMMarker CreateSquareMarkerPerSpecs()
{
  var squareMarker = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.BlueRGB, 5, SimpleMarkerStyle.Square) as CIMVectorMarker;
  CIMMarkerPlacementAlongLineSameSize markerPlacement2 = new CIMMarkerPlacementAlongLineSameSize()
  {
    AngleToLine = true,
    Endings = PlacementEndings.Custom,
    OffsetAlongLine = 45,
    PlacementTemplate = new double[] { 60 },
  };
  squareMarker.MarkerPlacement = markerPlacement2;
  return squareMarker;
}