Parsing Input Data for well-formedness

When building an XML file from external data, we need to validate that each
input string is well-formed.  The specific situation is a Loan Type field
which returns "A&D".  Before we populate our XML file, we need to convert
this to "A&D".  Otherwise the XSLT will complain and not render the
final page.

Before we build a utility class for checking/correcting these (all?!?) input
strings, i have to ask the obvious -- has anyone already created something
like this?  Certainly there are many other characters we will need to
consider, and we'll have to watch out for double-escaping things
(A&D).  

Must i reinvent this wheel?

Thanks,
Marty


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