Lepo.i18n

Internationalization library for .NET applications.

Add multilingual support to WPF, WinForms, or CLI apps. JSON, YAML, and RESX resources with Dependency Injection.

Created in Poland by Leszek Pomianowski and open-source community.

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Table of Contents

• Table of Contents
• Why This Library?
• Get Started
  • Install the Packages
• How to Use
  • 1. Register Localizations
  • 2. Localize in XAML
  • 3. Change Culture at Runtime
• Packages
• API Reference
  • LocalizationBuilder Methods
  • WPF XAML Extensions
  • Culture Management
• Maintainers
• Support
• License

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Why This Library?

Traditional .NET localization with resource files requires ceremony and scattered configuration:

// Traditional approach - manual resource loading
ResourceManager rm = new("MyApp.Resources.Strings", typeof(Program).Assembly);
CultureInfo culture = new("pl-PL");
string translated = rm.GetString("HelloWorld", culture) ?? "Hello World";

With Lepo.i18n, localizations are registered once and consumed anywhere - including directly in XAML:

// Lepo.i18n with Dependency Injection
services.AddStringLocalizer(b =>
{
    b.SetCulture("pl-PL");
    b.FromResource<Translations>(new CultureInfo("pl-PL"));
    b.FromResource<Translations>(new CultureInfo("en-US"));
});

<!-- Bind directly in XAML -->
<TextBlock Text="{i18n:StringLocalizer 'Hello World'}" />

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Get Started

Install the Packages

dotnet add package Lepo.i18n

Pick additional packages based on your needs:

# Microsoft.Extensions.DependencyInjection integration
dotnet add package Lepo.i18n.DependencyInjection

# Load translations from JSON files
dotnet add package Lepo.i18n.Json

# WPF markup extensions
dotnet add package Lepo.i18n.Wpf

NuGet: https://www.nuget.org/packages/Lepo.i18n

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How to Use

1. Register Localizations

WPF Application (without DI)

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        this.UseStringLocalizer(b =>
        {
            b.SetCulture(new CultureInfo("pl-PL"));
            b.FromResource<Translations>(new CultureInfo("pl-PL"));
            b.FromResource<Translations>(new CultureInfo("en-US"));
        });
    }
}

Generic Host with Dependency Injection

IHost host = Host.CreateDefaultBuilder()
    .ConfigureServices((context, services) =>
    {
        services.AddStringLocalizer(b =>
        {
            b.SetCulture("pl-PL");
            b.FromResource<Translations>(new CultureInfo("pl-PL"));
            b.FromJson(assembly, "Resources.Translations-en.json", new CultureInfo("en-US"));
        });
    })
    .Build();

Loading from JSON files

services.AddStringLocalizer(b =>
{
    b.SetCulture("en-US");
    b.FromJson(assembly, "Resources.en-US.json", new CultureInfo("en-US"));
    b.FromJson(assembly, "Resources.pl-PL.json", new CultureInfo("pl-PL"));
});

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2. Localize in XAML

Add the i18n XML namespace and use the StringLocalizer markup extension:

<Window
    xmlns:i18n="http://schemas.lepo.co/i18n/2022/xaml">

    <StackPanel>
        <!-- Simple localization -->
        <TextBlock Text="{i18n:StringLocalizer 'Hello World'}" />

        <!-- With string format arguments -->
        <TextBlock Text="{i18n:StringLocalizer 'Test {0}, of {1}!', Arg1='What?', Arg2='No'}" />

        <!-- In any content property -->
        <CheckBox Content="{i18n:StringLocalizer 'Enable notifications'}" />
    </StackPanel>
</Window>

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3. Change Culture at Runtime

WPF Application

Application.Current.SetLocalizationCulture(new CultureInfo("en-US"));

With ILocalizationCultureManager (DI)

public class SettingsViewModel(ILocalizationCultureManager cultureManager)
{
    public void SwitchToEnglish()
    {
        cultureManager.SetCulture("en-US");
    }
}

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Packages

Package	Description
Lepo.i18n	Core library - localization builder, provider, and YAML support
Lepo.i18n.DependencyInjection	IServiceCollection integration with IStringLocalizer
Lepo.i18n.Json	Load translations from embedded or external JSON files
Lepo.i18n.Wpf	WPF markup extensions (StringLocalizer, PluralStringLocalizer)

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API Reference

LocalizationBuilder Methods

Method	Description
SetCulture(CultureInfo)	Set the default culture
SetCulture(string)	Set the default culture by name
AddLocalization(LocalizationSet)	Add a localization set manually
FromResource<T>(CultureInfo)	Load from embedded RESX resource
FromJson(path, CultureInfo)	Load from an embedded JSON file
FromJson(assembly, path, CultureInfo)	Load from a JSON file in a specific assembly
FromYaml(assembly, path, CultureInfo)	Load from an embedded YAML file

WPF XAML Extensions

Extension	Description
{i18n:StringLocalizer 'key'}	Localize a string in XAML
{i18n:PluralStringLocalizer ...}	Localize with singular/plural forms

Culture Management

Method	Description
app.UseStringLocalizer(Action)	Configure localizations for a WPF app
app.SetLocalizationCulture(CultureInfo)	Change culture at runtime (WPF)
services.AddStringLocalizer(Action)	Register localizations via DI
ILocalizationCultureManager.SetCulture()	Change culture via DI service

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Maintainers

• Leszek Pomianowski (@pomianowski)

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Support

For support, please open a GitHub issue. We welcome bug reports, feature requests, and questions.

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License

This project is licensed under the terms of the MIT open source license. Please refer to the LICENSE file for the full terms.

You can use it in private and commercial projects. Keep in mind that you must include a copy of the license in your project.