Is there a way of setting culture for a whole application? All current threads and new threads?

Question

In .NET 4.5, you can use the CultureInfo.DefaultThreadCurrentCulture property to change the culture of an AppDomain.

For versions prior to 4.5 you have to use reflection to manipulate the culture of an AppDomain. There is a private static field on CultureInfo (m_userDefaultCulture in .NET 2.0 mscorlib, s_userDefaultCulture in .NET 4.0 mscorlib) that controls what CurrentCulture returns if a thread has not set that property on itself.

This does not change the native thread locale and it is probably not a good idea to ship code that changes the culture this way. It may be useful for testing though.

This gets asked a lot. Basically, no there isn't, not for .NET 4.0. You have to do it manually at the start of each new thread (or ThreadPool function). You could perhaps store the culture name (or just the culture object) in a static field to save having to hit the DB, but that's about it.

If you are using resources, you can manually force it by:

Resource1.Culture = new System.Globalization.CultureInfo("fr"); 

In the resource manager, there is an auto generated code that is as follows:

/// <summary>
///   Overrides the current thread's CurrentUICulture property for all
///   resource lookups using this strongly typed resource class.
/// </summary>
[global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
internal static global::System.Globalization.CultureInfo Culture {
    get {
        return resourceCulture;
    }
    set {
        resourceCulture = value;
    }
}

Now every time you refer to your individual string within this resource, it overrides the culture (thread or process) with the specified resourceCulture.

You can either specify language as in "fr", "de" etc. or put the language code as in 0x0409 for en-US or 0x0410 for it-IT. For a full list of language codes please refer to: Language Identifiers and Locales

For .NET 4.5 and higher, you should use:

var culture = new CultureInfo("en-US");
CultureInfo.DefaultThreadCurrentCulture = culture;
CultureInfo.DefaultThreadCurrentUICulture = culture;

Actually you can set the default thread culture and UI culture, but only with Framework 4.5+

I put in this static constructor

static MainWindow()
{
  CultureInfo culture = CultureInfo
    .CreateSpecificCulture(CultureInfo.CurrentCulture.Name);
  var dtf = culture.DateTimeFormat;
  dtf.ShortTimePattern = (string)Microsoft.Win32.Registry.GetValue(
    "HKEY_CURRENT_USER\\Control Panel\\International", "sShortTime", "hh:mm tt");
  CultureInfo.DefaultThreadCurrentUICulture = culture;
}

and put a breakpoint in the Convert method of a ValueConverter to see what arrived at the other end. CultureInfo.CurrentUICulture ceased to be en-US and became instead en-AU complete with my little hack to make it respect regional settings for ShortTimePattern.

Hurrah, all is well in the world! Or not. The culture parameter passed to the Convert method is still en-US. Erm, WTF?! But it's a start. At least this way

• you can fix the UI culture once when your app loads
• it's always accessible from CultureInfo.CurrentUICulture
• string.Format("{0}", DateTime.Now) will use your customised regional settings

If you can't use version 4.5 of the framework then give up on setting CurrentUICulture as a static property of CultureInfo and set it as a static property of one of your own classes. This won't fix default behaviour of string.Format or make StringFormat work properly in bindings then walk your app's logical tree to recreate all the bindings in your app and set their converter culture.