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);
});