Question

I’m working with visual studio 2008 developing software for windows CE 6.0, compact framework.

I’m having this “strange?” trouble with isNumeric method. Is there another better way to do this job? Why is getting me an exception? (two in facts…both of type FormatException)

Thank you

dim tmpStr as object = "Hello"
if isNumeric(tmpStr) then    // EXCEPTIONs on this line
    // It's a number
else
    // it's a string
end if

Answer 1

Even though the FormatException isn’t listed in the documentation of IsNumeric it is indeed one of the exceptions that can be thrown. The circumstances under which it will be thrown are

• Passed a string value
• The string doesn’t have an 0x or &H prefix

I couldn’t find any rationale for this behavior though. The only way I was even able to discern it was by digging through the implementation in reflector.

The best way to work around it seems to be to define a wrapper method

Module Utils
  Public Function IsNumericSafe(ByVal o As Object) As Boolean
    Try
      Return IsNumeric(o)
    Catch e As FormatException
      Return False
    End Try
  End Function
End Module