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](https://ArcGIS.github.io/arcgis-pro-sdk/images/Symbology/line-marker-angle.png)
/// </summary>
{
  //Create a line symbol with the markers placed at a 45 degree angle.
  //Create a marker from the "|" character.  This is the marker that will be used to render the line layer.
  //Note: Run withing QueuedTask
  var lineMarker = SymbolFactory.Instance.ConstructMarker(124, "Agency FB", "Regular", 12);

  //Default line symbol which will be modified 
  CIMLineSymbol lineSymbolWithMarkersAtAngle = 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
  lineSymbolWithMarkersAtAngle.SymbolLayers[0] = lineMarker;
}