public IReadOnlyList<ElevationSurfaceLayer> GetElevationSurfaceLayers()

// retrieve the elevation surface layers in the map including the Ground
var surfaceLayers = map.GetElevationSurfaceLayers();

// retrieve the single ground elevation surface layer in the map
var groundSurfaceLayer = map.GetGroundElevationSurfaceLayer();

// determine the number of elevation sources in the ground elevation surface layer
int numberGroundSources = groundSurfaceLayer.Layers.Count;
// get the first elevation source layer from the ground elevation surface layer
var groundSourceLayer = groundSurfaceLayer.Layers.FirstOrDefault();

var surfaceLayers = map.GetElevationSurfaceLayers();
var surfaceLayer = surfaceLayers.FirstOrDefault(l => l.Name == "Surface2");

surfaceLayer = map.FindElevationSurfaceLayer(layerUri);