[c#] How to use localization in C#

I just can't seem to get localization to work.

I have a class library. Now I want to create resx files in there, and return some values based on the thread culture.

How can I do that?

It's quite simple, actually. Create a new resource file, for example Strings.resx. Set Access Modifier to Public. Use the apprioriate file template, so Visual Studio will automatically generate an accessor class (the name will be Strings, in this case). This is your default language.

Now, when you want to add, say, German localization, add a localized resx file. This will be typically Strings.de.resx in this case. If you want to add additional localization for, say, Austria, you'll additionally create a Strings.de-AT.resx.

Now go create a string - let's say a string with the name HelloWorld. In your Strings.resx, add this string with the value "Hello, world!". In Strings.de.resx, add "Hallo, Welt!". And in Strings.de-AT.resx, add "Servus, Welt!". That's it so far.

Now you have this generated Strings class, and it has a property with a getter HelloWorld. Getting this property will load "Servus, Welt!" when your locale is de-AT, "Hallo, Welt! when your locale is any other de locale (including de-DE and de-CH), and "Hello, World!" when your locale is anything else. If a string is missing in the localized version, the resource manager will automatically walk up the chain, from the most specialized to the invariant resource.

You can use the ResourceManager class for more control about how exactly you are loading things. The generated Strings class uses it as well.

Great answer by F.Mörk. But if you want to update translation, or add new languages once the application is released, you're stuck, because you always have to recompile it to generate the resources.dll.

Here is a solution to manually compile a resource dll. It uses the resgen.exe and al.exe tools (installed with the sdk).

Say you have a Strings.fr.resx resource file, you can compile a resources dll with the following batch:

resgen.exe /compile Strings.fr.resx,WpfRibbonApplication1.Strings.fr.resources 
Al.exe /t:lib /embed:WpfRibbonApplication1.Strings.fr.resources /culture:"fr" /out:"WpfRibbonApplication1.resources.dll"
del WpfRibbonApplication1.Strings.fr.resources
pause

Be sure to keep the original namespace in the file names (here "WpfRibbonApplication1")

In general you put your translations in resource files, e.g. resources.resx.

Each specific culture has a different name, e.g. resources.nl.resx, resources.fr.resx, resources.de.resx, …

Now the most important part of a solution is to maintain your translations. In Visual Studio install the Microsoft MAT tool: Multilingual App Toolkit (MAT). Works with winforms, wpf, asp.net (core), uwp, …

In general, e.g. for a WPF solution, in the WPF project

• Install the Microsoft MAT extension for Visual Studio.
• In the Solution Explorer, navigate to your Project > Properties > AssemblyInfo.cs
• Add in AssemblyInfo.cs your default, neutral language (in my case English): [assembly: System.Resources.NeutralResourcesLanguage("en")]
• Select your project in Solution Explorer and in Visual Studio, from the top menu, click "Tools" > "Multilingual App Toolkit" > "Enable Selection", to enable MAT for the project.
  • Now Right mouse click on the project in Solution Explorer, select "Multilingual App Toolkit" > "Add translation languages…" and select the language that you want to add translations for. e.g. Dutch.

What you will see is that a new folder will be created, called "MultilingualResources" containing a ....nl.xlf file.

The only thing you now have to do is:

1. add your translation to your default resources.resx file (in my case English)
2. Translate by clicking the .xlf file (NOT the .resx file) as the .xlf files will generate/update the .resx files.

(the .xlf files should open with the "Multilingual Editor", if this is not the case, right mouse click on the .xlf file, select "Open With…" and select "Multilingual Editor".

Have fun! now you can also see what has not been translated, export translations in xlf to external translation companies, import them again, recycle translations from other projects etc...

More info:

• Using the Multilingual App Toolkit 4.0: https://docs.microsoft.com/windows/uwp/design/globalizing/use-mat
• Multilingual App Toolkit blog, visit: http://aka.ms/matblog
• Multilingual App Toolkit User Voice feature voting site, visit: http://aka.ms/matvoice

In my case

[assembly: System.Resources.NeutralResourcesLanguage("ru-RU")]

in the AssemblyInfo.cs prevented things to work as usual.

In addition to @Eric Bole-Feysot answer:

Thanks to satellite assemblies, localization can be created based on .dll/.exe files. This way:

• source code (VS project) could be separated from language project,
• adding a new language does not require recompiling the project,
• translation could be made even by the end-user.

There is a little known tool called LSACreator (free for non-commercial use or buy option) which allows you to create localization based on .dll/.exe files. In fact, internally (in language project's directory) it creates/manages localized versions of resx files and compiles an assembly in similar way as @Eric Bole-Feysot described.

In addition @Fredrik Mörk's great answer on strings, to add localization to a form do the following:

• Set the form's property "Localizable" to true
• Change the form's Language property to the language you want (from a nice drop-down with them all in)
• Translate the controls in that form and move them about if need be (squash those really long full French sentences in!)

Edit: This MSDN article on Localizing Windows Forms is not the original one I linked ... but might shed more light if needed. (the old one has been taken away)

A fix and elaboration of @Fredrik Mörk answer.

• Add a strings.resx Resource file to your project (or a different filename)
• Set Access Modifier to Public (in the opened strings.resx file tab)
• Add a string resouce in the resx file: (example: name Hello, value Hello)
• Save the resource file

Visual Studio auto-generates a respective strings class, which is actually placed in strings.Designer.cs. The class is in the same namespace that you would expect a newly created .cs file to be placed in.

This code always prints Hello, because this is the default resource and no language-specific resources are available:

Console.WriteLine(strings.Hello);

Now add a new language-specific resource:

• Add strings.fr.resx (for French)
• Add a string with the same name as previously, but different value: (name Hello, value Salut)

The following code prints Salut:

Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo("fr-FR");
Console.WriteLine(strings.Hello);

What resource is used depends on Thread.CurrentThread.CurrentUICulture. It is set depending on Windows UI language setting, or can be set manually like in this example. Learn more about this here.

You can add country-specific resources like strings.fr-FR.resx or strings.fr-CA.resx.

The string to be used is determined in this priority order:

• From country-specific resource like strings.fr-CA.resx
• From language-specific resource like strings.fr.resx
• From default strings.resx

Note that language-specific resources generate satellite assemblies.

Also learn how CurrentCulture differs from CurrentUICulture here.

ResourceManager and .resx are bit messy.

You could use Lexical.Localization¹ which allows embedding default value and culture specific values into the code, and be expanded in external localization files for futher cultures (like .json or .resx).

public class MyClass
{
    /// <summary>
    /// Localization root for this class.
    /// </summary>
    static ILine localization = LineRoot.Global.Type<MyClass>();

    /// <summary>
    /// Localization key "Ok" with a default string, and couple of inlined strings for two cultures.
    /// </summary>
    static ILine ok = localization.Key("Success")
            .Text("Success")
            .fi("Onnistui")
            .sv("Det funkar");

    /// <summary>
    /// Localization key "Error" with a default string, and couple of inlined ones for two cultures.
    /// </summary>
    static ILine error = localization.Key("Error")
            .Format("Error (Code=0x{0:X8})")
            .fi("Virhe (Koodi=0x{0:X8})")
            .sv("Sönder (Kod=0x{0:X8})");

    public void DoOk()
    {
        Console.WriteLine( ok );
    }

    public void DoError()
    {
        Console.WriteLine( error.Value(0x100) );
    }
}

¹ (I'm maintainer of that library)