public sealed class MosaicLayer : CompositeLayer, ArcGIS.Desktop.Core.IMetadataInfo, IInternalMosaicLayer, ILayerContainer, IMetadataSource, ITableDefinitionQueries, System.ComponentModel.INotifyPropertyChanged  

MosaicLayer mosaicLayer = null;
string url = @"C:\Images\countries.gdb\Italy";
await QueuedTask.Run(() =>
{
  // Create a mosaic layer using a path to a mosaic dataset.
  // Note: You can create a mosaic layer from a url, project item, or data connection.
  mosaicLayer = LayerFactory.Instance.CreateLayer(new Uri(url), aMap) as MosaicLayer;
});

  // 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);
  });