abp-localization

ABP Localization Skill

Trigger

User asks about localization, internationalization, i18n, localization resources, JSON localization files, culture, L[] helper, multi-language support, or text translation in ABP Framework.

Core Concepts

ABP's localization system extends Microsoft.Extensions.Localization with:

• Localization Resources — Group related localization strings
• JSON Files — Store translations in embedded JSON files
• Culture Fallback — Automatic fallback to default culture
• Virtual File System — Embed resources in assemblies
• L[] Helper — Convenient access to localized strings

Creating a Localization Resource

Resource Class

public class BookStoreResource
{
}

Plain class — no base class needed.

Register the Resource

[DependsOn(typeof(AbpLocalizationModule))]
public class MyModule : AbpModule
{
    public override void ConfigureServices(ServiceConfigurationContext context)
    {
        // Add embedded JSON files from assembly
        Configure<AbpVirtualFileSystemOptions>(options =>
        {
            options.FileSets.AddEmbedded<MyModule>("YourRootNamespace");
        });

        // Register localization resource
        Configure<AbpLocalizationOptions>(options =>
        {
            options.Resources
                .Add<BookStoreResource>("en")  // Default culture
                .AddVirtualJson("/Localization/Resources/BookStore");
        });
    }
}

JSON File Structure

/Localization/Resources/BookStore/en.json:

{
  "culture": "en",
  "texts": {
    "HelloWorld": "Hello World!",
    "Menu:Home": "Home",
    "Menu:BookStore": "Book Store",
    "Permission:BookStore_Author_Create": "Creating a new author"
  }
}

/Localization/Resources/BookStore/tr.json:

{
  "culture": "tr",
  "texts": {
    "HelloWorld": "Merhaba Dünya!",
    "Menu:Home": "Ana Sayfa",
    "Menu:BookStore": "Kitap Mağazası",
    "Permission:BookStore_Author_Create": "Yeni yazar oluşturma"
  }
}

Important:

• Every file must define culture code — ABP ignores files without it
• texts section contains key-value pairs
• Keys can have spaces

Nested Keys and Arrays

Nested Objects

{
  "culture": "en",
  "texts": {
    "Hello": {
      "World": "Hello World!"
    }
  }
}

Access: L["Hello__World"] (double underscore separates parent from child)

Arrays

{
  "culture": "en",
  "texts": {
    "Hi": [
      { "Bye": "Bye World!" },
      { "Hello": "Hello World!" }
    ]
  }
}

Access: L["Hi__0"] → "Bye World!", L["Hi__1"] → "Hello World!"

Multiple Files per Culture

Split large modules into multiple files:

Localization/
└── MyResource/
    ├── en.json            ← base / shared strings
    ├── en_Authors.json    ← Author feature strings
    ├── en_Books.json      ← Book feature strings
    └── en_Users.json      ← User feature strings

Files are automatically merged. Useful for large modules where splitting by feature keeps files manageable.

Using Localization

In Application Services / Domain Services

public class BookAppService : ApplicationService
{
    public BookAppService()
    {
        LocalizationResource = typeof(BookStoreResource);
    }

    public void DoWork()
    {
        var text = L["HelloWorld"];
        var localized = L["Menu:BookStore"];
    }
}

In Any Service (via IStringLocalizer)

public class MyService : ITransientDependency
{
    private readonly IStringLocalizer<BookStoreResource> _localizer;

    public MyService(IStringLocalizer<BookStoreResource> localizer)
    {
        _localizer = localizer;
    }

    public void DoWork()
    {
        var text = _localizer["HelloWorld"];
    }
}

In Controllers

public class BookController : AbpController
{
    public BookController()
    {
        LocalizationResource = typeof(BookStoreResource);
    }

    public IActionResult Index()
    {
        ViewData["Title"] = L["Menu:BookStore"];
        return View();
    }
}

In Razor Views

@using Volo.Abp.Localization
@inject IStringLocalizer<BookStoreResource> L

<h1>@L["HelloWorld"]</h1>
<p>@L["Menu:BookStore"]</p>

Culture Configuration

Default Culture

Configure<AbpLocalizationOptions>(options =>
{
    options.Languages.Add(new LanguageInfo("en", "en", "English"));
    options.Languages.Add(new LanguageInfo("tr", "tr", "Türkçe"));
    options.DefaultResourceType = typeof(BookStoreResource);
});

Culture Fallback

If a key doesn't exist in the current culture, ABP falls back to:

1. Default culture (e.g., "en")
2. Returns the key itself if not found anywhere

URL-Based Localization

ABP supports culture in URL path:

• /en/Home → English
• /tr/Home → Turkish

Configure in appsettings.json:

{
  "App": {
    "SupportedCultures": ["en", "tr", "de"]
  }
}

Best Practices

1. One resource per module — Keep localization scoped to modules
2. Use prefixes in keys — Menu:, Permission:, Error: for organization
3. Split large files — Use multiple files per culture for big modules
4. Always define culture — ABP ignores JSON files without culture field
5. Use Virtual File System — Embed JSON files in assembly for distribution
6. Set LocalizationResource — In base classes to avoid repetition
7. Localize everything user-facing — Menu items, error messages, permission names
8. Use consistent key naming — Module:Feature:Key pattern

Common Patterns

Base App Service with Localization

public abstract class BookStoreAppService : ApplicationService
{
    protected BookStoreAppService()
    {
        LocalizationResource = typeof(BookStoreResource);
    }
}

Localized Permission Names

myGroup.AddPermission(
    "BookStore_Author_Create",
    LocalizableString.Create<BookStoreResource>("Permission:BookStore_Author_Create")
);

Localized Exception Messages

throw new UserFriendlyException(L["Error:InsufficientStock"]);

Related

• Virtual File System — Embedding resources
• Localization — Culture in URLs
• Microsoft.Extensions.Localization — Microsoft's localization docs