Program.cs

using Microsoft.AspNetCore.Localization;
using Microsoft.Extensions.Options;
using System.Globalization;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllersWithViews();

// Đăng ký localization
builder.Services.AddLocalization(options => options.ResourcesPath = "Resources");

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

    options.DefaultRequestCulture = new RequestCulture("en");
    options.SupportedCultures = supportedCultures;
    options.SupportedUICultures = supportedCultures;

    // Cho phép đọc từ query ?culture=vi hoặc cookie
    options.RequestCultureProviders.Insert(0, new QueryStringRequestCultureProvider());
    options.RequestCultureProviders.Insert(1, new CookieRequestCultureProvider());
});

var app = builder.Build();

var locOptions = app.Services.GetService<IOptions<RequestLocalizationOptions>>();
app.UseRequestLocalization(locOptions.Value);

app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();

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

app.Run();