如何在String.ToUpper（）中忽略撇号？

Question

In french lot of City have apostrophe in their name. Like "rue de l'église"

We Use a converter to Write it in Full UpperCase in almost every UI Part.

But string.ToUpper seem to have a bug because we get "RUE DE L'église" instead of the "RUE DE L'ÉGLISE" we are supposed to get.

Can you explain why? anyway to get the expected result?

My converter look like this

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value != null)
        {
            var res = CultureInfo.CurrentCulture.TextInfo.ToTitleCase(value.ToString().ToUpper());
            return res;
        }

        return String.Empty;
    }

Answer 1

You've probably hit a cornercase that wasn't considered, or the behavior is "correct".

The documentation of TextInfo.ToTitleCase states:

Converts the specified string to title case ( except for words that are entirely in uppercase, which are considered to be acronyms ).

(my emphasis)

The code probably doesn't consider non-letter characters, so the presence of the apostrophe makes this a word that isn't all uppercase, and thus the letters after the first is converted to lowercase.

The question is, isn't this behavior correct? The presence of the apostrophe means this is not an acronym, and thus it shouldn't follow the rule that the all-uppercase words (acronyms) follow. The correct behavior for non-acronym words is that the first letter gets to be uppercase, the rest lowercase (regardless of their current state).

Regardless of this, there is additional documentation further down on the same page:

As illustrated above, the ToTitleCase method provides an arbitrary casing behavior which is not necessarily linguistically correct. A linguistically correct solution would require additional rules, and the current algorithm is somewhat simpler and faster. We reserve the right to make this API slower in the future.

Which means they've actually documented that it doesn't necessarily do exactly what people want, only provide a good-enough(tm) approach to the problem.

In light of all this I'd say the method behaves exactly as documented.

Answer 2

ToTitleCase() does not do what you want. It capitalizes the first character of each word. What you want is just plain string.ToUpper() :

Console.WriteLine("rue de l'église".ToUpper());

Output:

RUE DE L'ÉGLISE

---

ToTitleCase() :

Console.WriteLine(CultureInfo.GetCultureInfo("fr-fr").TextInfo.ToTitleCase("rue de l'église"));

Output

Rue De L'église

---

Combining ToTitleCase() and ToUpper() causes this weird behavior that you describe, since ToTitleCase() tries to lowercase every other character than the first (except for words that are all uppercase and considered acronyms, according to the documentation )

Answer 3

May be the issue is in your "CurrentCulture" or the "ToTitleCase"?

Tell me your "CultureInfo" identifier ( System.Globalization.CultureInfo.CurrentCulture.ToString() ), so I could investigave more.

Answer 4

I have tried in VB and I have the same "problem".

The problem is linked to ToTitleCase() function because ToUpper() function work well.

I have tried in adding "chrétien" just after "église"

Dim s = "Rue de l'église chrétienne".ToUpper()
Dim res = CultureInfo.CurrentCulture.TextInfo.ToTitleCase(s)

res variable contains "RUE DE L'église CHRÉTIENNE"

You can see that the 'é' of "église" has not been converted but 'é' of "chrétien" has been converter to upper case !

The s variable contains "RUE DE L'ÉGLISE CHRÉTIENNE"

If I replace "église" by "eglise" (without accentued character), the res variable contains "RUE DE L'eglise CHRÉTIENNE"

We can see that the 'é' character has no impact on the conversion.

My Regional Setting is FR-FR.

I think that it is a bug because Microsoft doesn't respect correctly french language in which simple quote is part of language.

In waiting a Microsoft solution, you can implement following workaround :

Dim res
    = CultureInfo
        .CurrentCulture
            .TextInfo
                .ToTitleCase(s.replace("'","--"))
                    .replace("--","'")

In fact, if what you will is converting in TitleCase, you must remove the conversion to UpperCase.

The correct code would be

Dim s = "Rue de l--église chrétienne de l--hiver"
Dim res = CultureInfo.CurrentCulture.TextInfo
  .ToTitleCase(s.Replace("'", "--")).Replace("--", "'")

and res varaible contains "Rue De L'Église Chrétienne De L'Hiver" !