public RendererDefinition RendererDefinition {get; set;}

var flyrCreatnParam = new FeatureLayerCreationParams(new Uri(@"c:\data\world.gdb\cities"))
{
  Name = "World Cities",
  IsVisible = false,
  MinimumScale = 1000000,
  MaximumScale = 5000,
  // At 2.x - DefinitionFilter = new CIMDefinitionFilter()
  //{
  //  DefinitionExpression = "Population > 100000",
  //  Name = "More than 100k"
  //},
  DefinitionQuery = new DefinitionQuery(whereClause: "Population > 100000", name: "More than 100k"),
  RendererDefinition = new SimpleRendererDefinition()
  {
    SymbolTemplate = SymbolFactory.Instance.ConstructPointSymbol(
      CIMColor.CreateRGBColor(255, 0, 0), 8, SimpleMarkerStyle.Hexagon).MakeSymbolReference()
  }
};

var featureLayer = LayerFactory.Instance.CreateLayer<FeatureLayer>(
  flyrCreatnParam, map);

//Note: Call within QueuedTask.Run()
if (MapView.Active.Map == null) return;

//Get an existing Layer. This layer has a symbol you want to use in a new layer.
var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>()
      .Where(l => l.ShapeType == esriGeometryType.esriGeometryPoint).FirstOrDefault();
//This is the renderer to use in the new Layer
var renderer = lyr.GetRenderer() as CIMSimpleRenderer;
//Set the Dataconnection for the new layer
Geodatabase geodatabase = new Geodatabase(
  new FileGeodatabaseConnectionPath(new Uri(@"E:\Data\Admin\AdminData.gdb")));
FeatureClass featureClass = geodatabase.OpenDataset<FeatureClass>("Cities");
var dataConnection = featureClass.GetDataConnection();
//Create the definition for the new feature layer
var featureLayerParams = new FeatureLayerCreationParams(dataConnection)
{
  RendererDefinition = new SimpleRendererDefinition(renderer.Symbol),
  IsVisible = true,
};
//create the new layer
LayerFactory.Instance.CreateLayer<FeatureLayer>(
  featureLayerParams, MapView.Active.Map);

var url = @"https://geoeventsample1.esri.com:6443/arcgis/rest/services/LABus/StreamServer";
var uri = new Uri(url, UriKind.Absolute);
//Must be on QueuedTask!
var createParams = new FeatureLayerCreationParams(uri)
{
  RendererDefinition = new SimpleRendererDefinition()
  {
    SymbolTemplate = SymbolFactory.Instance.ConstructPointSymbol(
                        ColorFactory.Instance.BlueRGB,
                        12,
                 SimpleMarkerStyle.Pushpin).MakeSymbolReference()
  }
};
var streamLayer = LayerFactory.Instance.CreateLayer<StreamLayer>(
                    createParams, map);