void deleteBookmark(PdfBookmarkCollections bookmarks, PdfBookmark toBeDeleted)
		{
			if (bookmarks == null || bookmarks.Count < 1 || toBeDeleted == null)
			{
				return;
			}

			if (bookmarks.Contains(toBeDeleted))
			{
				int idx = bookmarks.IndexOf(toBeDeleted);
				bookmarks.ToList().Remove(toBeDeleted);
				try
				{
					bookmarks.DeleteAt(idx);
				}catch (Exception ex)
				{
					MessageUtil.Alter("删除书签失败:" + ex.Message);
				}

			}

			foreach (PdfBookmark b in bookmarks)
			{
				deleteBookmark(b.Childs, toBeDeleted);
			}
		}