public void SelectLayers( 
   IReadOnlyCollection<Layer> layers
)

public void SelectAllFeatureLayersInTOC()
{
  //Get the active map view.
  var mapView = MapView.Active;
  if (mapView == null)
    return;

  //Zoom to the selected layers in the TOC
  var featureLayers = mapView.Map.Layers.OfType<FeatureLayer>();
  mapView.SelectLayers(featureLayers.ToList());
}