public static void refresh_thumbnails()
{
DirectoryInfo d = new DirectoryInfo(configurations.GetAbsoluteThumbnailPath());
FileInfo[] files = d.GetFiles();
window_manager.thumbnails.Clear();
foreach (FileInfo f in files)
window_manager.thumbnails.Add(Convert.ToInt32(f.Name.Split(new char[] { '.' })[0]),
new BitmapImage(new Uri(configurations.GetAbsoluteThumbnailPath() + f.Name)));
}