C# 4 and .NET 4

namespace system.Globalization ❘ 571
Possibly the most important class in the System.Globalization namespace is CultureInfo. CultureInfo
represents a culture and defines calendars, formatting of numbers and dates, and sorting strings used with
the culture.
The class RegionInfo represents regional settings (such as the currency) and shows whether the region
is using the metric system. Some regions can use multiple languages. One example is the region of Spain,
which has Basque (eu-ES), Catalan (ca-ES), Spanish (es-ES), and Galician (gl-ES) cultures. Similar to one
region having multiple languages, one language can be spoken in different regions; for example, Spanish is
spoken in Mexico, Spain, Guatemala, Argentina, and Peru, to name only a few countries.
Later in this chapter, you see a sample application that demonstrates these characteristics of cultures and regions.
specific, neutral, and invariant Cultures
When using cultures in the .NET Framework, you have to differentiate between three types: specific,
neutral, and invariant cultures.
A specific culture is associated with a real, existing culture defined with
RFC 1766, as you saw in the preceding section. A specific culture can be
mapped to a neutral culture. For example, de is the neutral culture of the
specific cultures de-AT, de-DE, de-CH, and others. de is shorthand for
the German language (Deutsch); AT, DE, and CH are shorthand for the
countries Austria, Germany, and Switzerland, respectively.
When translating applications, it is typically not necessary to do
translations for every region; not much difference exists between the
German language in the countries Austria and Germany. Instead of using
specific cultures, you can use a neutral culture to localize applications.
The invariant culture is independent of a real culture. When storing
formatted numbers or dates in files, or sending them across a network to
a server, using a culture that is independent of any user settings is the best
option.
Figure 22-2 shows how the culture types relate to each other.
CurrentCulture and CurrentUiCulture
When you set cultures, you need to differentiate between a culture for the user interface and a culture
for the number and date formats. Cultures are associated with a thread, and with these two culture types,
two culture settings can be applied to a thread. The Thread class has the properties CurrentCulture and
CurrentUICulture. The property CurrentCulture is for setting the culture that is used with formatting
and sort options, whereas the property CurrentUICulture is used for the language of the user interface.
Users can change the default setting of the CurrentCulture by using the Regional and Language options
in the Windows Control Panel (see Figure 22-3). With this configuration, it is also possible to change the
default number, the time, and the date format for the culture.
The CurrentUICulture does not depend on this configuration. The CurrentUICulture setting depends
on the language of the operating system. There is one exception, though: If a multi-language user interface
(MUI) is installed with Windows 7, Windows Vista or Windows XP, it is possible to change the language of
the user interface with the regional configuration, and this influences the property CurrentUICulture.
These settings make a very good default, and in many cases, there is no need to change the default behavior.
If the culture should be changed, you can easily do this by changing both cultures of the thread to, say, the
Spanish culture, as shown in this code snippet:
System.Globalization.CultureInfo ci = new
System.Globalization.CultureInfo("es-ES");
System.Threading.Thread.CurrentThread.CurrentCulture = ci;
System.Threading.Thread.CurrentThread.CurrentUICulture = ci;
Invariant
figure 22-2
de
en
de-AT
de-DE
de-CH
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