EnvelopeGenerator/EnvelopeGenerator.Web/Middleware/CultureMiddleware.cs

using EnvelopeGenerator.Web.Extensions;
using EnvelopeGenerator.Web.Models;
using Microsoft.AspNetCore.Localization;
using Microsoft.Extensions.Options;
using System.Globalization;

namespace EnvelopeGenerator.Web.Middleware;

public class CultureMiddleware
{
    private readonly RequestDelegate _next;
    private readonly MultiCulture _cultures;

    public CultureMiddleware(RequestDelegate next, IOptions<MultiCulture> culturesOpt)
    {
        _next = next;
        _cultures = culturesOpt.Value;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        var cookieName = CookieRequestCultureProvider.DefaultCookieName;
        var cookieValue = context.Request.Cookies[cookieName];

        if (!_cultures.Languages.Contains(cookieValue))
        {
            var requestCulture = context.GetCultureByAcceptLanguage()?.Name;
            var culture = _cultures.GetOrDefault(requestCulture);
            var cultureInfo = culture.Info ?? new CultureInfo(culture.Language);

            context.Response.Cookies.SetCulture(culture.Language);
            CultureInfo.CurrentCulture = cultureInfo;
            CultureInfo.CurrentUICulture = cultureInfo;
        }

        await _next(context);
    }
}