public bool CanGetZs()

{
    TinLayer tinLayer = map.GetLayersAsFlattenedList().OfType<TinLayer>().FirstOrDefault();
    //Note: This method must be called on the MCT
    MapPoint mapPoint = MapView.Active.Map.CalculateFullExtent().Center; //Any Map Point
    Polyline polyline = PolylineBuilderEx.CreatePolyline(mapView.Extent); //Any Polyline

    if (tinLayer.CanGetZs())
    {
        // get z value for a mapPoint
        var zResult = tinLayer.GetZs(mapPoint);
        if (zResult.Status == SurfaceZsResultStatus.Ok)
        {
            // cast to a mapPoint
            var mapPointZ = zResult.Geometry as MapPoint;
            var z = mapPointZ.Z;
        }

        // get z values for a polyline
        zResult = tinLayer.GetZs(polyline);
        if (zResult.Status == SurfaceZsResultStatus.Ok)
        {
            // cast to a mapPoint
            var polylineZ = zResult.Geometry as Polyline;
        }
    }
}

{
  // Note: Needs QueuedTask to run
  {
    if (tinLayer.CanGetZs())
    {
      // get z value for a mapPoint
      var zResult = tinLayer.GetZs(mapPoint);
      if (zResult.Status == SurfaceZsResultStatus.Ok)
      {
        // cast to a mapPoint
        var mapPointZ = zResult.Geometry as MapPoint;
        var z = mapPointZ.Z;
      }

      // get z values for a polyline
      zResult = tinLayer.GetZs(polyline);
      if (zResult.Status == SurfaceZsResultStatus.Ok)
      {
        // cast to a Polyline
        var polylineZ = zResult.Geometry as Polyline;
      }
    }
  }
}