.NET 8.0 + ASP.NET Core(MVC) で実装するクエリベースローカライズ処理（多国言語対応）

.NET 8.0 の ASP.NET Core アプリ(MVC)でローカライズ機能を使い、多国言語対応したサンプルを作成しました。
ソースコードは GitHub で公開しています。

ソースコード構成

今回使った Visual Studio プロジェクトテンプレートは、Visual Studio 2022 + .NET 8 + ASP.NET Core MVC、HTTPS無し。

ソースコード変更内容を解説

WebApplication1/Controllers/HomeController.cs

コントローラーに、Resources/Controllers/HomeController.**.resx リソースを参照する処理を追加。


using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Localization;
using System.Diagnostics;
using WebApplication1.Models;

namespace WebApplication1.Controllers
{
  public class HomeController : Controller
  {
    private readonly ILogger<HomeController> _logger;
    private readonly IStringLocalizer<HomeController> _localizer;

    public HomeController(ILogger<HomeController> logger, IStringLocalizer<HomeController> localizer)
    {
      _logger = logger;
      _localizer = localizer;
    }

    public IActionResult Index()
    {
      ViewBag.Message = _localizer["ControllerString1"];
      return View();
    }

    public IActionResult Privacy()
    {
      return View();
    }

    [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
    public IActionResult Error()
    {
      return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
    }
  }
}

using Microsoft.AspNetCore.Mvc;

using Microsoft.Extensions.Localization;

using System.Diagnostics;

using WebApplication1.Models;

namespace WebApplication1.Controllers

{

public class HomeController : Controller

{

private readonly ILogger<HomeController> _logger;

private readonly IStringLocalizer<HomeController> _localizer;

public HomeController(ILogger<HomeController> logger, IStringLocalizer<HomeController> localizer)

{

_logger = logger;

_localizer = localizer;

}

public IActionResult Index()

{

ViewBag.Message = _localizer["ControllerString1"];

return View();

}

public IActionResult Privacy()

{

return View();

}

[ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]

public IActionResult Error()

{

return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });

}

WebApplication1/Views/Home/Index.cshtml

元々Top画面に表示されてた文は削除。
ビューに、Resources/Views/Home/Index.**.resx リソースを参照する処理を追加。


@using Microsoft.AspNetCore.Mvc.Localization

@inject IViewLocalizer Localizer

@{
  ViewData["Title"] = Localizer["About"];
}

<h1>Localizer["String1"]: @Localizer["ViewString1"]</h1>
<h1>ViewBag.Message: @ViewBag.Message</h1>

@using Microsoft.AspNetCore.Mvc.Localization

@inject IViewLocalizer Localizer

ViewData["Title"] = Localizer["About"];

}

<h1>Localizer["String1"]: @Localizer["ViewString1"]</h1>

<h1>ViewBag.Message: @ViewBag.Message</h1>

WebApplication1/Program.cs

Asp.net core 標準のローカライズ機能を開始処理に追加。
対応した言語は ja en のみ。


using Microsoft.AspNetCore.Mvc.Razor;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddLocalization(options => options.ResourcesPath = "Resources");

builder.Services.Configure<RequestLocalizationOptions>(options =>
{
  var supportedCultures = new[] { "ja", "en" };
  options.SetDefaultCulture(supportedCultures[0])
    .AddSupportedCultures(supportedCultures)
    .AddSupportedUICultures(supportedCultures);
});

builder.Services.AddMvc()
  .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
  .AddDataAnnotationsLocalization();

// Add services to the container.
builder.Services.AddControllersWithViews()
  .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
  .AddDataAnnotationsLocalization();

builder.Services.Configure<RequestLocalizationOptions>(options =>
{
  var supportedCultures = new[]
  {
    new System.Globalization.CultureInfo("en"),
    new System.Globalization.CultureInfo("ja")
  };

  options.DefaultRequestCulture = new Microsoft.AspNetCore.Localization.RequestCulture("ja");
  options.SupportedCultures = supportedCultures;
  options.SupportedUICultures = supportedCultures;
});

var app = builder.Build();
app.UseRequestLocalization();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
  app.UseExceptionHandler("/Home/Error");
}
app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapControllerRoute(
  name: "default",
  pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();

using Microsoft.AspNetCore.Mvc.Razor;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddLocalization(options => options.ResourcesPath = "Resources");

builder.Services.Configure<RequestLocalizationOptions>(options =>

{

var supportedCultures = new[] { "ja", "en" };

options.SetDefaultCulture(supportedCultures[0])

.AddSupportedCultures(supportedCultures)

.AddSupportedUICultures(supportedCultures);

});

builder.Services.AddMvc()

.AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)

.AddDataAnnotationsLocalization();

// Add services to the container.

builder.Services.AddControllersWithViews()

.AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)

.AddDataAnnotationsLocalization();

builder.Services.Configure<RequestLocalizationOptions>(options =>

{

var supportedCultures = new[]

{

new System.Globalization.CultureInfo("en"),

new System.Globalization.CultureInfo("ja")

};

options.DefaultRequestCulture = new Microsoft.AspNetCore.Localization.RequestCulture("ja");

options.SupportedCultures = supportedCultures;

options.SupportedUICultures = supportedCultures;

});

var app = builder.Build();

app.UseRequestLocalization();

// Configure the HTTP request pipeline.

if (!app.Environment.IsDevelopment())

{

app.UseExceptionHandler("/Home/Error");

}

app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapControllerRoute(

name: "default",

pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();

WebApplication1/Resources/Controllers/HomeController.en.resxWebApplication1/Resources/Controllers/HomeController.ja.resx

テスト用リソースを追加したのみ。

WebApplication1/Resources/Views/Home/Index.en.resxWebApplication1/Resources/Views/Home/Index.ja.resx

テスト用リソースを追加したのみ。