public CIMStroke ConstructStroke( 
   CIMColor color,
   double width,
   SimpleLineStyle lineStyle
)

{
  //Create a simple 2D rectangle graphic and apply simple fill and
  //outline symbols.

  //Note: Must be on QueuedTask.Run

  //Build 2D envelope geometry
  Coordinate2D rec_ll = new Coordinate2D(1.0, 4.75);
  Coordinate2D rec_ur = new Coordinate2D(3.0, 5.75);

  Envelope rec_env = EnvelopeBuilderEx.CreateEnvelope(rec_ll, rec_ur);

  //Set symbology, create and add element to layout
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
    ColorFactory.Instance.BlackRGB, 5.0, SimpleLineStyle.Solid);
  CIMPolygonSymbol polySym = SymbolFactory.Instance.ConstructPolygonSymbol(
    ColorFactory.Instance.GreenRGB, SimpleFillStyle.DiagonalCross, outline);


  GraphicElement recElm = ElementFactory.Instance.CreateGraphicElement(
    layout, rec_env, polySym, "New Rectangle");
  //Or use Predefined shape
  GraphicElement recElm2 = ElementFactory.Instance.CreatePredefinedShapeGraphicElement(
                            layout, PredefinedShape.Rectangle, rec_env, polySym,
                            "New Rectangle2");
}

{
    CIMStroke outline = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlueRGB, 2.0, SimpleLineStyle.Solid);
    CIMPolygonSymbol fillWithOutline = SymbolFactory.Instance.ConstructPolygonSymbol(ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid, outline);
}

/// <summary>
/// Constructs a picture fill with the specified parameters.
/// ![ConstructPictureFill](https://ArcGIS.github.io/arcgis-pro-sdk/images/Symbology/ConstructPictureFill.png)
/// </summary>
{
  //Note: Run withing QueuedTask
  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(CIMColor.CreateRGBColor(110, 110, 110), 2.0, SimpleLineStyle.Solid);
  //picture
  var imgPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), @"Images\CaliforniaEmblem.png");
  var pictureFill = SymbolFactory.Instance.ConstructPictureFill(imgPath, 64);

  List<CIMSymbolLayer> symbolLayers = new()
  {
    outline,
    pictureFill
  };
  CIMPolygonSymbol pictureFillPolygonSymbol = new CIMPolygonSymbol() { SymbolLayers = symbolLayers.ToArray() };
  //To apply the symbol to a polygon feature layer
  //var renderer = theLayer.GetRenderer() as CIMSimpleRenderer;
  //renderer.Symbol = pictureFillPolygonSymbol.MakeSymbolReference();
  //theLayer.SetRenderer(renderer);
}

/// <summary>
/// Constructs a water fill of specific color, waterbody size and wave strength. This fill can be used on polygon feature classes in a Scene view only.
/// ![ConstructWaterFill](https://ArcGIS.github.io/arcgis-pro-sdk/images/Symbology/waterAnimation.gif)
/// </summary>
{
  //Note: Run withing QueuedTask

  CIMStroke outline = SymbolFactory.Instance.ConstructStroke(CIMColor.CreateRGBColor(49, 49, 49, 50.0), 2.0, SimpleLineStyle.Solid);
  var waterFill = SymbolFactory.Instance.ConstructWaterFill(CIMColor.CreateRGBColor(3, 223, 252), WaterbodySize.Large, WaveStrength.Rippled);
  List<CIMSymbolLayer> symbolLayers = new List<CIMSymbolLayer>
    {
              outline,
              waterFill
    };
  CIMPolygonSymbol waterFillPolygonSymbol = new CIMPolygonSymbol() { SymbolLayers = symbolLayers.ToArray() };
  //To apply the symbol to a polygon feature layer
  //var renderer = theLayer.GetRenderer() as CIMSimpleRenderer;
  //renderer.Symbol = waterFillPolygonSymbol.MakeSymbolReference();
  //theLayer.SetRenderer(renderer);
}