public string ThumbnailImagePath {get; set;}

public Task<Bookmark> AddBookmarkFromCameraAsync(Camera camera, string name)
{
  return QueuedTask.Run(() =>
  {
    //Set properties for Camera
    CIMViewCamera cimCamera = new CIMViewCamera()
    {
      X = camera.X,
      Y = camera.Y,
      Z = camera.Z,
      Scale = camera.Scale,
      Pitch = camera.Pitch,
      Heading = camera.Heading,
      Roll = camera.Roll
    };

    //Create new CIM bookmark and populate its properties
    var cimBookmark = new CIMBookmark() { Camera = cimCamera, Name = name, ThumbnailImagePath = "" };

    //Get the active map view.
    var mapView = MapView.Active;
    if (mapView == null)
      return null;

    //Add a new bookmark for the active map.
    return mapView.Map.AddBookmark(cimBookmark);
  });
}