CODEWITHSUNDEEP
c#.netstringcomparisoncase-insensitive
Robert Harvey
Robert Harvey

Reputation: 180858

Using InvariantCultureIgnoreCase instead of ToUpper for case-insensitive string comparisons

On this page, a commenter writes:

Do NOT ever use .ToUpper to insure comparing strings is case-insensitive.

Instead of this: 

type.Name.ToUpper() == (controllerName.ToUpper() + "Controller".ToUpper()))

Do this: 

type.Name.Equals(controllerName + "Controller", 
     StringComparison.InvariantCultureIgnoreCase)

Why is this way preferred?

Upvotes: 15

Views: 14101

Answers (2)

Gabriele Petrioli
Gabriele Petrioli

Reputation: 196142

Here is the answer in details .. The Turkey Test (read section 3)

As discussed by lots and lots of people, the "I" in Turkish behaves differently than in most languages. Per the Unicode standard, our lowercase "i" becomes "İ" (U+0130 "Latin Capital Letter I With Dot Above") when it moves to uppercase. Similarly, our uppercase "I" becomes "ı" (U+0131 "Latin Small Letter Dotless I") when it moves to lowercase.

Fix: Again, use an ordinal (raw byte) comparer, or invariant culture for comparisons unless you absolutely need culturally based linguistic comparisons (which give you uppercase I's with dots in Turkey)

And according to Microsoft you should not even be using the Invariant... but the Ordinal... (New Recommendations for Using Strings in Microsoft .NET 2.0)

Upvotes: 19

Nick Craver
Nick Craver

Reputation: 630549

In short, it's optimized by the CLR (less memory as well).

Further, uppercase comparison is more optimized than ToLower(), if that tiny degree of performance matters.

In response to your example there is a faster way yet:

String.Equals(type.Name, controllerName + "Controller", 
              StringComparison.InvariantCultureIgnoreCase);

Upvotes: 10

Related Questions