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();
}

{
    // retrieve the elevation surface layers in the map 
    var surfaceLayers = map.GetElevationSurfaceLayers();
    // find a specific elevation surface layer by its URI
    var surfaceLayer = surfaceLayers.FirstOrDefault(l => l.Name == "Surface2");
    // or use the FindElevationSurfaceLayer method, passing the layer URI
    surfaceLayer = map.FindElevationSurfaceLayer("layerUri");
}