Hi,
Currently in ArcGIS Runtime SDK for .NET v100.1 (i.e. UWP, WPF, and Xamarin) we display the raster data at the native raster resolution. The alternative is to re-sample the raster as you zoom out. For a future release we are investigating implementing re-sampling dynamically as you zoom in/out, and allowing you as the developer to generate the resampled data via the API and persist that alongside the raster dataset. The persisted approach is usually referred to as pyramids.
You can achieve the same approach today by using ArcGIS Pro or ArcMap to generate pyramids for your raster data in advance and then use that raster within your ArcGIS Runtime apps. For more information see Build Pyramids—Data Management toolbox | ArcGIS Desktop.
Cheers
Mike