public DefinitionQuery DefinitionQuery {get; set;}

{
    var flyrCreatnParam = new FeatureLayerCreationParams(new Uri(@"c:\data\world.gdb\cities"))
    {
        Name = "World Cities",
        IsVisible = false,
        MinimumScale = 1000000,
        MaximumScale = 5000,
        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()
        }
    };
    //Note: Needs QueuedTask to run
    var featureLayerWithParams = LayerFactory.Instance.CreateLayer<FeatureLayer>(flyrCreatnParam, map);
}

{
    //The catalog path of the feature layer to add to the map
    var featureClassUriDefinition = new Uri(@"C:\Data\Admin\AdminData.gdb\USA\cities");
    //Define the Feature Layer's parameters.
    var layerParamsQueryDefn = new FeatureLayerCreationParams(featureClassUriDefinition)
    {
        IsVisible = true,
        DefinitionQuery = new DefinitionQuery(whereClause: "STATE_NAME = 'California'", name: "CACities")
    };
    //Note: Needs QueuedTask to run
    //Create the layer with the feature layer parameters and add it to the active map
    var createdFCWithQueryDefn = LayerFactory.Instance.CreateLayer<FeatureLayer>(layerParamsQueryDefn, MapView.Active.Map);
}

{
  // Note: call within QueuedTask.Run()
  {
    //Must be on the QueuedTask
    var url = "https://geoeventsample1.esri.com:6443/arcgis/rest/services/AirportTraffics/StreamServer";
    var lyrCreateParam = new FeatureLayerCreationParams(new Uri(url))
    {
      IsVisible = true,
      DefinitionQuery = new DefinitionQuery(whereClause: "RWY = '29L'", name: "Runway")
    };

    streamLayer = LayerFactory.Instance.CreateLayer<StreamLayer>(lyrCreateParam, map);
  }
}