public Nullable<double> max {get; set;}

//If a raster dataset has statistics, you can create a raster layer and get these statistics by accessing the colorizer.
await QueuedTask.Run(() =>
{
  //Accessing the raster layer
  var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<BasicRasterLayer>().FirstOrDefault();
  //Getting the colorizer
  var colorizer = lyr.GetColorizer() as CIMRasterStretchColorizer;
  //Accessing the statistics
  var stats = colorizer.StretchStats;
  var max = stats.max;
  var min = stats.min;
});