VB6 "IsNumeric()" behaviour in Windows 8/Windows 2012 - windows-8

Question

Using a VB6 app on Windows 7 both lines return TRUE, because somehow the decimal separator is not considered:
IsNumeric("123.45")
IsNumeric("123,45")
On Windows 8 or Windows 2012, the same code returns TRUE or FALSE depending on the regional settings. Considering the comma as decimal separator defined in regional settings, then:
IsNumeric("123.45") returns FALSE
IsNumeric("123,45") returns TRUE
Is there any way to restore the "old" behaviour without recompiling the app?

Answer 1

This is not a new issue with which version of Windows you are using. It's always been based on the locale settings of the machine.
What I did for my application is I made my own functions:
Public Function IsNumber(ByRef Expression As Variant) As Boolean
Select Case VarType(Expression)
Case vbInteger, vbLong, vbSingle, vbDouble, vbCurrency, vbDate, vbBoolean, vbDecimal, vbByte
IsNumber = True
Case vbString
Dim Negative As Boolean
Dim Number As Boolean
Dim Period As Boolean
Dim Positive As Boolean
Dim X As Long
For X = 1& To Len(Expression)
Select Case Mid$(Expression, X, 1&)
Case "0" To "9"
Number = True
Case "-"
If Period Or Number Or Negative Or Positive Then Exit Function
Negative = True
Case "."
If Period Or Exponent Then Exit Function
Period = True
Case "E", "e"
If Not Number Then Exit Function
If Exponent Then Exit Function
Exponent = True
Number = False
Negative = False
Period = False
Case "+"
If Not Exponent Then Exit Function
If Number Or Negative Or Positive Then Exit Function
Positive = True
Case vbSpace, vbTab, vbVerticalTab, vbCr, vbLf, vbFormFeed
If Period Or Number Or Exponent Or Negative Then Exit Function
Case Else
Exit Function
End Select
Next X
IsNumber = Number
End Select
End Function
If you're dealing with strings explicitly, then you could simplify that function. And also you likely don't want to deal with exponents, so this might be more suited:
Public Function IsNumber(ByRef Expression As String) As Boolean
Dim Negative As Boolean
Dim Number As Boolean
Dim Period As Boolean
Dim X As Long
For X = 1& To Len(Expression)
Select Case Mid$(Expression, X, 1&)
Case "0" To "9"
Number = True
Case "-"
If Period Or Number Or Negative Then Exit Function
Negative = True
Case "."
If Period Then Exit Function
Period = True
Case vbSpace, vbTab, vbVerticalTab, vbCr, vbLf, vbFormFeed
If Period Or Number Or Negative Then Exit Function
Case Else
Exit Function
End Select
Next X
IsNumber = Number
End Function
When you are in need of converting the number, use Str() instead of CLng()/CInt()/CDbl()/CSng()/Val(). Str() treats periods as decimals regardless of locale, just like my IsNumber() function above.