public void OnImageChanged(uint viewerId) { Viewer viewer = _viewerList.Get(viewerId); if ((viewer != null) && (_api != null)) { string imageId = _api.GetImageID(viewerId); viewer.ImageId = imageId; if (viewer.HasMarker) { viewer.HasMarker = false; List <Viewer> markerViewers = _viewerList.MarkerViewers; if (markerViewers.Count == 0 && _crossCheck != null) { _crossCheck.Dispose(); _crossCheck = null; } } } }