public class CIMSolidStroke : CIMStroke, 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;
}

/// <summary>
/// Create a line symbol with a dash and two markers. <br/>
/// In this pattern of creating this symbol, a [CIMVectorMarker](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic6176.html) object is created as a new [CIMSymbolLayer](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic5503.html).
/// The circle and square markers created by [ContructMarker](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic12350.html) method is then assigned to the [MarkerGraphics](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic6188.html) property of the CIMVectorMarker. 
/// When using this method, the CIMVectorMarker's [Frame](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic6187.html) property needs to be set to the [CIMMarker](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic3264.html) object's Frame. 
/// Similarly, the CIMVectorMarker's [Size](https://pro.arcgis.com/en/pro-app/sdk/api-reference/#topic3284.html) property needs to be set to the CIMMarker object's size.
/// </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> CreateLineDashTwoMarkers2Async()
{
  return QueuedTask.Run<CIMLineSymbol>(() =>
  {
    //default line symbol that will get modified.
    var dash2MarkersLine = new CIMLineSymbol();
    //circle marker to be used in our line symbol as a layer
    var circleMarker = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.BlackRGB, 5, SimpleMarkerStyle.Circle) as CIMVectorMarker;
    //circle marker to be used in our line symbol as a layer
    var squareMarker = SymbolFactory.Instance.ConstructMarker(ColorFactory.Instance.BlueRGB, 5, SimpleMarkerStyle.Square) as CIMVectorMarker;
    //Create the array of layers that make the new line symbol
    CIMSymbolLayer[] mySymbolLyrs =
          {
                new CIMSolidStroke() //dash line
                {
                    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
                        }
                    }
                },
                new CIMVectorMarker() //circle marker
                {
                    MarkerGraphics = circleMarker.MarkerGraphics,
                    Frame = circleMarker.Frame, //need to match the CIMVector marker's frame to the circleMarker's frame.
                    Size = circleMarker.Size,    //need to match the CIMVector marker's size to the circleMarker's size.                    
                   MarkerPlacement = new CIMMarkerPlacementAlongLineSameSize()
                   {
                       AngleToLine = true,
                       Offset = 0,
                       Endings = PlacementEndings.Custom,
                       OffsetAlongLine = 15,
                       PlacementTemplate = new double[] {60},
                   }

                },
                new CIMVectorMarker() //square marker
                {
                   MarkerGraphics = squareMarker.MarkerGraphics,
                   Frame = squareMarker.Frame, //need to match the CIMVector marker's frame to the squareMarker frame.
                   Size = squareMarker.Size, //need to match the CIMVector marker's size to the squareMarker size.
                   MarkerPlacement = new CIMMarkerPlacementAlongLineSameSize()
                   {
                       AngleToLine = true,
                       Endings = PlacementEndings.Custom,
                       OffsetAlongLine = 45,
                       PlacementTemplate = new double[] {60},
                   }
                }
      };
    dash2MarkersLine.SymbolLayers = mySymbolLyrs;
    return dash2MarkersLine;
  });

}