public class RasterLayerCreationParams : LayerCreationParams 

// Create a new stretch colorizer definition using default constructor.
StretchColorizerDefinition stretchColorizerDef = new StretchColorizerDefinition();
var rasterLayerCreationParams = new RasterLayerCreationParams(new Uri(url))
{
  ColorizerDefinition = stretchColorizerDef,
  Name = layerName,
  MapMemberIndex = 0
};
await QueuedTask.Run(() =>
{
  // Create a raster layer using the colorizer definition created above.
  // Note: You can create a raster layer from a url, project item, or data connection.
  RasterLayer rasterLayerfromURL =
    LayerFactory.Instance.CreateLayer<RasterLayer>(rasterLayerCreationParams, aMap);
});

// Create a new colorizer definition using default constructor.
StretchColorizerDefinition stretchColorizerDef = new StretchColorizerDefinition();
var rasterLayerCreationParams = new RasterLayerCreationParams(new Uri(url))
{
  Name = layerName,
  ColorizerDefinition = stretchColorizerDef,
  MapMemberIndex = 0

};
await QueuedTask.Run(() =>
{
  // Create a mosaic layer using the colorizer definition created above.
  // Note: You can create a mosaic layer from a url, project item, or data connection.
  MosaicLayer newMosaicLayer =
    LayerFactory.Instance.CreateLayer<MosaicLayer>(rasterLayerCreationParams, aMap);
});

// Create a new colorizer definition using default constructor.
StretchColorizerDefinition stretchColorizerDef = new StretchColorizerDefinition();
var rasterLayerCreationParams = new RasterLayerCreationParams(new Uri(url))
{
  Name = layerName,
  ColorizerDefinition = stretchColorizerDef,
  MapMemberIndex = 0
};
await QueuedTask.Run(() =>
{
  // Create an image service layer using the colorizer definition created above.
  ImageServiceLayer imageServiceLayer =
    LayerFactory.Instance.CreateLayer<ImageServiceLayer>(rasterLayerCreationParams, aMap);
});