Internationalization support for .NET applications built around a simple provider model.
Catalyst.Internationalization handles locale selection, resource caching, fallback behavior, and integration with .NET hosting. It does not define where translations come from. Applications provide an ILocaleProvider, which can load resources from JSON, embedded files, a database, an API, or anywhere else that makes sense for the application.
The package is designed for dependency injection and is marked as NativeAOT-compatible.
dotnet add package Catalyst.InternationalizationA locale provider represents the resources for one loaded locale. Implement ILocaleProvider, populate the dictionary when LoadLocaleAsync is called, and register the provider with the service collection.
using Catalyst.Internationalization;
public sealed class AppLocaleProvider : Dictionary<string, string>, ILocaleProvider {
public Task LoadLocaleAsync(
Locale locale,
CancellationToken cancellationToken = default) {
Clear();
switch (locale) {
case Locale.en_US:
this["hello"] = "Hello!";
break;
case Locale.es_ES:
this["hello"] = "¡Hola!";
break;
}
return Task.CompletedTask;
}
}Register the provider and Catalyst internationalization services:
using Catalyst.Internationalization.Extensions;
services.AddLocaleProvider<AppLocaleProvider>();
services.AddInternationalization();ILocaleProvider is registered as a scoped service. The localization host creates a new scope when a locale needs to be loaded, snapshots the provider's resources into a LocaleMap, and caches that map for later requests.
Only one locale provider is used. AddLocaleProvider<T>() uses first-registration-wins behavior, so later locale-provider registrations will not replace an existing provider.
LocalizationService uses CultureInfo.CurrentUICulture to select the locale automatically:
public sealed class ExampleService {
private readonly LocalizationService _localization;
public ExampleService(LocalizationService localization) {
_localization = localization;
}
public async Task<string> GetGreetingAsync(
CancellationToken cancellationToken = default) {
return await _localization.GetAsync("hello", cancellationToken);
}
}If the current UI culture does not contain the requested key, the configured default locale is used as a fallback. If the key still cannot be found, the key itself is returned.
For explicit locale selection or exception behavior, use LocalizationHost.GetAsync directly:
string value = await host.GetAsync(
Locale.es_ES,
"hello",
fallback: Locale.en_US,
throwExceptions: true,
cancellationToken);ILocaleProvider is intentionally small:
public interface ILocaleProvider : IReadOnlyDictionary<string, string> {
Task LoadLocaleAsync(
Locale locale,
CancellationToken cancellationToken = default);
}The provider owns resource loading. Catalyst only requires that, after LoadLocaleAsync completes, enumerating the provider returns the key/value resources for that locale.
Because providers are scoped, implementations may safely keep state associated with the locale currently being loaded. The host copies that state into its own cached LocaleMap before the provider scope is disposed.
Loaded locale maps are kept in an IMemoryCache through LocalizationCache.
The default cache duration is one hour. When an entry expires, the next request for that locale causes the provider to load it again.
Provider failures are also cached temporarily as an empty locale map. This prevents a failing resource source from being hit repeatedly on every localization request. Cancellation is never swallowed and continues to propagate to the caller.
LocaleHelper converts between Catalyst locales and .NET CultureInfo values:
Locale locale = LocaleHelper.FromCultureInfo(CultureInfo.CurrentUICulture);
CultureInfo culture = LocaleHelper.ToCultureInfo(Locale.en_US);Exact culture names are preferred. When an exact locale is not available, Catalyst falls back by language where a mapping exists. For example, an unsupported English regional culture falls back to en-US.
Catalyst currently defines locales for Arabic, Bengali, German, English, Spanish, Persian, French, Hindi, Indonesian, Italian, Japanese, Korean, Dutch, Polish, Portuguese, Russian, Tagalog/Filipino, Turkish, Ukrainian, Urdu, Vietnamese, and Chinese, with regional variants where defined by the Locale enum.
Unless configured otherwise:
- Default locale:
en-US - Cache duration: 1 hour
- Missing key: returns the requested key
- Provider lifetime: scoped
- Locale maps: cached in memory
The package is built with NativeAOT compatibility enabled and verifies AOT compatibility of its references. Locale-provider registration is generic and preserves the public constructors required by .NET dependency injection.
No assembly scanning or runtime provider discovery is required. Providers are registered explicitly:
services.AddLocaleProvider<AppLocaleProvider>();CatalystUI Internationalization is licensed under the Apache License 2.0.
Copyright © 2026 CatalystUI LLC.