Found a low surrogate char without a preceding high...

Question

I have such code: Debug.WriteLine(message); Debug.Flush(); Flush method raises next Exception: Server was unable to process request. --> Found a low surrogate char without a preceding high surrogate at index: 118. The input may not be in this encoding, or may not contain valid Unicode (UTF-16) characters. message - is a regular string containing only ASCII lower part characters. I assume, that it may contain some character combination which may not be encoded in UTF-16 by streamwriter. But have no idea how to fight this case. Please, help.