Usually, there is no such thing as a double-byte character in .NET -- it uses UTF-16 Unicode, in which *every* character is expressed by two bytes.
However, if you're reading a file or stream that is coming in as a multi-byte character set (something like Shift-JIS or UTF-8), then you'll have to write code to convert it to UTF-16, or use one of the built-in Convert methods (in the case of UTF-8).
Chip H.