CultureInfo.CurrentCulture and CultureInfo.CurrentUICulture

The CultureInfo.CurrentUICulture property is a per-thread setting that returns the current user interface culture. This property is used by the ResourceManager class to look up culture-specific resources at run time. By default, it corresponds to the user UI language.

The user UI language determines the default language of menus and dialog boxes, messages, INF files, and help files. This setting controls the language in which the UI is presented. It is only present if you have the MUI version of Windows (which is to say that you have Windows with the multilanguage files installed).

This setting is found on the second tab of the Windows XP/Server 2003 Regional and Language Options dialog and in the middle of the first tab of the Windows 2000 Regional Options dialog. The setting is per-user and changing it requires a logoff to take effect.

The CultureInfo.CurrentCulture property is a per-thread setting that determines the default formats for dates, times, currency, and numbers, the sorting order of text, string comparisons, and casing. The CurrentCulture property is not a language setting. It contains only data related to the standard settings for a geographical region. Therefore, the CurrentCulture property can only be set to a specific culture or to the InvariantCulture. By default, it corresponds to the default user locale.

The list of locales can be thought of as a big group of defaults that are grouped by many language/region pairings, which you can see in the first tab Regional and Language Options Control Panel applet. Several of the settings are customizable, particularly the various formats. The setting is per-user and when you change the setting, it is effective immediately.

The contents of this post are from SDK and a post from Michael Kaplan.