public CIMLineSymbol ConstructLineSymbol( 
   CIMColor color,
   double width,
   SimpleLineStyle lineStyle
)

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

/// <summary>
/// Create a line symbol with the markers placed at a 45 degree angle. <br/>  
/// ![LineSymbolAngleMarker](http://Esri.github.io/arcgis-pro-sdk/images/Symbology/line-marker-angle.png)
/// </summary>
/// <returns></returns>
internal static Task<CIMLineSymbol> CreateMyMarkerLineSymbolAsync()
{
    return QueuedTask.Run<CIMLineSymbol>(() =>
    {
        //Create a marker from the "|" character.  This is the marker that will be used to render the line layer.
        var lineMarker = SymbolFactory.Instance.ConstructMarker(124, "Agency FB", "Regular", 12);

        //Default line symbol which will be modified 
        var blackSolidLineSymbol = SymbolFactory.Instance.ConstructLineSymbol(ColorFactory.Instance.BlackRGB, 2, SimpleLineStyle.Solid);

        //Modifying the marker to align with line
        //First define "markerplacement"
        CIMMarkerPlacementAlongLineSameSize markerPlacement = new CIMMarkerPlacementAlongLineSameSize()
        {
            AngleToLine = true,
            PlacementTemplate = new double[] { 5 }
        };
        //assign the markerplacement to the marker
        lineMarker.MarkerPlacement = markerPlacement;
        //angle the marker if needed
        lineMarker.Rotation = 45;

        //assign the marker as a layer to the line symbol
        blackSolidLineSymbol.SymbolLayers[0] = lineMarker;

        return blackSolidLineSymbol;
    });
}