On Avoiding ToLower

A reader writes in to ask if uppercase is OK, why isn't using ToLower?

On Avoiding ToLower
I found Bill McCarthy's article on VB's operators ["Load Up With VB's Operators," August 2007] interesting. However, I was curious why Bill asserted that it's OK to convert each string to uppercase, but you should avoid using ToLower. Can you tell me what is wrong with using ToLower, please?

Premjit (Maz) Mazumdar
received by e-mail

It depends a lot on the locale. For example, in some locales é will uppercase to E, yet E will lowercase to e. If you compare the lowercase of E to é, it won't be a match. Uppercase, on the other hand, will generally match. The use of ToUpper can be handy in circumstances like this one:

Select Case myString.ToUpper
	Case "ABC"
	Case "DEF", "FGH"
	Case "IJK"
' ...

You can also specify the culture to use:

mystring.ToUpper
(Globalization.CultureInfo.InvariantCulture)

For the most part, using ToUpper won't cause any problems, but the ToUpper call does cause a new string to be created, so it can get expensive if you use it repeatedly. With some locales, and with special characters such as the German letter ß, ToUpper won't give the same results as the Compare or Equals methods. That's why I said in the article to consider using String.Compare instead. Consider how things change if we write the ToUpper code sample using String.Compare or String.Equals:

If String.Equals(myString, "ABC",
StringComparison.OrdinalIgnoreCase) Then
ElseIf String.Equals(myString, "DEF", 
         StringComparison.OrdinalIgnoreCase) _
	OrElse String.Equals(myString, "FGH",
StringComparison.OrdinalIgnoreCase) _ 		
    Then
ElseIf String.Equals(myString, "IJK", 
   StringComparison.OrdinalIgnoreCase) Then
' ...
End If

I think I'd much rather suffer a little performance hit for the sake of readability.

--Bill McCarthy


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