public class SymbolStyleItem : StyleItem, System.ComponentModel.INotifyPropertyChanged  

//Create a simple 2D point graphic and apply an existing point style item as the symbology.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D point geometry  
  Coordinate2D coord2D = new Coordinate2D(2.0, 10.0);

  //(optionally) Reference a point symbol in a style
  StyleProjectItem ptStylePrjItm = Project.Current.GetItems<StyleProjectItem>()
                                .FirstOrDefault(item => item.Name == "ArcGIS 2D");
  SymbolStyleItem ptSymStyleItm = ptStylePrjItm.SearchSymbols(
                                         StyleItemType.PointSymbol, "City Hall")[0];
  CIMPointSymbol pointSym = ptSymStyleItm.Symbol as CIMPointSymbol;
  pointSym.SetSize(50);

  //Set symbology, create and add element to layout

  //An alternative simple symbol is also commented out below.
  //This would eliminate the four optional lines of code above that
  //reference a style.

  //CIMPointSymbol pointSym = SymbolFactory.Instance.ConstructPointSymbol(
  //                  ColorFactory.Instance.RedRGB, 25.0, SimpleMarkerStyle.Star);  
  //At 2.x - GraphicElement ptElm =
  //                    LayoutElementFactory.Instance.CreatePointGraphicElement(
  //                                        layout, coord2D, pointSym);

  GraphicElement ptElm = ElementFactory.Instance.CreateGraphicElement(
                                 container, coord2D.ToMapPoint(), pointSym);
  ptElm.SetName("New Point");
});

//Create a simple 2D line graphic and apply an existing line
//style item as the symbology.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2d line geometry
  List<Coordinate2D> plCoords = new List<Coordinate2D>();
  plCoords.Add(new Coordinate2D(1, 8.5));
  plCoords.Add(new Coordinate2D(1.66, 9));
  plCoords.Add(new Coordinate2D(2.33, 8.1));
  plCoords.Add(new Coordinate2D(3, 8.5));
  //At 2.x - Polyline linePl = PolylineBuilder.CreatePolyline(plCoords);
  Polyline linePl = PolylineBuilderEx.CreatePolyline(plCoords);

  //(optionally) Reference a line symbol in a style
  StyleProjectItem lnStylePrjItm = Project.Current.GetItems<StyleProjectItem>()
                                .FirstOrDefault(item => item.Name == "ArcGIS 2D");
  SymbolStyleItem lnSymStyleItm = lnStylePrjItm.SearchSymbols(
                                StyleItemType.LineSymbol, "Line with 2 Markers")[0];
  CIMLineSymbol lineSym = lnSymStyleItm.Symbol as CIMLineSymbol;
  lineSym.SetSize(20);

  //Set symbology, create and add element to layout

  //An alternative simple symbol is also commented out below.
  //This would eliminate the four optional lines of code above that
  //reference a style.
  //
  //CIMLineSymbol lineSym = SymbolFactory.Instance.ConstructLineSymbol(
  //         ColorFactory.Instance.BlueRGB, 4.0, SimpleLineStyle.Solid);  
  //At 2.x - GraphicElement lineElm =
  //        LayoutElementFactory.Instance.CreateLineGraphicElement(
  //                                            layout, linePl, lineSym);

  GraphicElement lineElm = ElementFactory.Instance.CreateGraphicElement(
                                              container, linePl, lineSym);
  lineElm.SetName("New Line");
});

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

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D envelope geometry
  Coordinate2D rec_ll = new Coordinate2D(1.0, 4.75);
  Coordinate2D rec_ur = new Coordinate2D(3.0, 5.75);
  //At 2.x - Envelope rec_env = EnvelopeBuilder.CreateEnvelope(rec_ll, rec_ur);
  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);

  //At 2.x - GraphicElement recElm =
  //           LayoutElementFactory.Instance.CreateRectangleGraphicElement(
  //                                                  layout, rec_env, polySym);
  //         recElm.SetName("New Rectangle");
  //
  GraphicElement recElm = ElementFactory.Instance.CreateGraphicElement(
    container, rec_env, polySym, "New Rectangle");
  //Or use Predefined shape
  GraphicElement recElm2 = ElementFactory.Instance.CreatePredefinedShapeGraphicElement(
                            container, PredefinedShape.Rectangle, rec_env, polySym, 
                            "New Rectangle2");
});

public Task<SymbolStyleItem> GetSymbolFromStyleAsync(StyleProjectItem style, string key)
{
  return QueuedTask.Run(() =>
  {
    if (style == null)
        throw new System.ArgumentNullException();

    //Search for a specific point symbol in style
    SymbolStyleItem item = (SymbolStyleItem)style.LookupItem(StyleItemType.PointSymbol, key);
    return item;
  });
}

public Task<IList<SymbolStyleItem>> GetPointSymbolsFromStyleAsync(StyleProjectItem style, string searchString)
{
  if (style == null)
    throw new System.ArgumentNullException();

  //Search for point symbols
  return QueuedTask.Run(() => style.SearchSymbols(StyleItemType.PointSymbol, searchString));
}

public Task<IList<SymbolStyleItem>> GetLineSymbolsFromStyleAsync(StyleProjectItem style, string searchString)
{
  if (style == null)
    throw new System.ArgumentNullException();

  //Search for line symbols
  return QueuedTask.Run(() => style.SearchSymbols(StyleItemType.LineSymbol, searchString));
}

public async Task<IList<SymbolStyleItem>> GetPolygonSymbolsFromStyleAsync(StyleProjectItem style, string searchString)
{
  if (style == null)
    throw new System.ArgumentNullException();

  //Search for polygon symbols
  return await QueuedTask.Run(() => style.SearchSymbols(StyleItemType.PolygonSymbol, searchString));
}