public Block Get(DocumentOwner owner) { if (_ids == null) { return(null); } BlockCollection collection = owner.Root; Block block = null; for (int i = _ids.Length - 1; i >= 0; i--) { int blockIndex = _ids[0]; Debug.Assert(collection != null); block = collection.GetNthBlock(blockIndex); collection = block as BlockCollection; } return(block); }