Startup.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Threading.Tasks;
using LocalizationDemo.Extensions.ValidationMetadataProvider;
using LocalizationDemo.Resources;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Localization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Localization;

namespace LocalizationDemo
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddLocalization(opt =>
            {
                opt.ResourcesPath = "Resources";
            });
            services.AddMvc(opt =>
            {
                opt.ModelMetadataDetailsProviders.Add(
                   new CustomValidationMetadataProvider(typeof(SharedResources)));
            })
                .SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
                .AddViewLocalization()
                .AddDataAnnotationsLocalization()
                .ConfigureModelBindingMessages();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            CultureInfo.DefaultThreadCurrentCulture = new CultureInfo("es");
            CultureInfo.DefaultThreadCurrentUICulture = new CultureInfo("es");

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRequestLocalization(opt =>
            {
                opt.RequestCultureProviders.Remove(opt.RequestCultureProviders.OfType<AcceptLanguageHeaderRequestCultureProvider>().First());
                opt.AddSupportedCultures("es", "en");
                opt.AddSupportedUICultures("es", "en");
                opt.SetDefaultCulture("es");
            });

            app.UseCookiePolicy();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Person}/{action=Edit}/{id?}");
            });
        }
    }
}