Efficient ISNUMERIC() replacements on SQL Server?

Question

So I just spent 5 hours troubleshooting a problem which turned out to be due not only to the old unreliable ISNUMERIC but it looks like my problem only appears

Answer 1

According to Microsoft support the only efficient way to replace UDF function is to write your own .NET function version.

Of course, if your database admin allows that :).

Mine doesn't :(.