public class SimpleRendererDefinition : RendererDefinition 

{
    //Define a simple renderer to draw the Point US Cities feature class.
    var simpleRender = new SimpleRendererDefinition
    {
        SymbolTemplate = SymbolFactory.Instance.ConstructPointSymbol(ColorFactory.Instance.RedRGB, 4.0, SimpleMarkerStyle.Circle).MakeSymbolReference()

    };
    //The catalog path of the feature layer to add to the map
    var featureClassUri = new Uri(@"C:\Data\Admin\AdminData.gdb\USA\cities");
    //Define the Feature Layer's parameters.
    var layerParams = new FeatureLayerCreationParams(featureClassUri)
    {
        //Set visibility
        IsVisible = true,
        //Set Renderer
        RendererDefinition = simpleRender,
    };
    //Create the layer with the feature layer parameters and add it to the active map
    //Note: Needs QueuedTask to run
    var createdFCWithRenderer = LayerFactory.Instance.CreateLayer<FeatureLayer>(layerParams, MapView.Active.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);
}

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