public string GetTextAt(int offset, int count) { if (offset < 0) { throw new ArgumentException("startOffset < 0"); } if (offset > TextLength) { throw new ArgumentException("startOffset > Length"); } if (count < 0) { throw new ArgumentException("count < 0"); } if (offset + count > TextLength) { throw new ArgumentException("offset + count is beyond EOF"); } return(buffer.GetTextAt(offset, count)); }