How do I determine if a Char is in some character set?

System.Text.Encoding can be used to determine some
encoding of a Char if that Char can be encoded in it. But
what if the char is not in that character set corresponding
to the encoding? For example, U+714A is a Chinese
character, but not in Big5 character set. I'll get the
encoding of '?' using Encoding class.

Any other more definitive/direct way to know if a Char
is in some character set?

Thanks.

Isaac Chen