Implemented POC for the language switch.

templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/BlazorClientHttpMessageHandler.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.JSInterop;
+using Volo.Abp.DependencyInjection;
+
+namespace MyCompanyName.MyProjectName.Blazor
+{
+    public class BlazorClientHttpMessageHandler : DelegatingHandler, ITransientDependency
+    {
+        private readonly IJSRuntime _jsRuntime;
+
+        public BlazorClientHttpMessageHandler(IJSRuntime jsRuntime)
+        {
+            _jsRuntime = jsRuntime;
+        }
+
+        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            await SetLanguageAsync(request, cancellationToken);
+
+            return await base.SendAsync(request, cancellationToken);
+        }
+
+        private async Task SetLanguageAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            var selectedLanguage = await _jsRuntime.InvokeAsync<string>(
+                "localStorage.getItem",
+                cancellationToken,
+                "Abp.SelectedLanguage"
+            );
+
+            if (!selectedLanguage.IsNullOrWhiteSpace())
+            {
+                request.Headers.AcceptLanguage.Clear();
+                request.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue(selectedLanguage));
+            }
+        }
+    }
+}

templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/MyProjectNameBlazorModule.cs

@@ -9,6 +9,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Volo.Abp;
 using Volo.Abp.AspNetCore.Components.WebAssembly;
 using Volo.Abp.Autofac;
+using Volo.Abp.Http.Client;
 using Volo.Abp.Http.Client.IdentityModel.WebAssembly;
 using Volo.Abp.Identity.Blazor;
 using Volo.Abp.Modularity;
@@ -24,6 +25,17 @@ namespace MyCompanyName.MyProjectName.Blazor
     )]
     public class MyProjectNameBlazorModule : AbpModule
     {
+        public override void PreConfigureServices(ServiceConfigurationContext context)
+        {
+            PreConfigure<AbpHttpClientBuilderOptions>(options =>
+            {
+                options.ProxyClientBuildActions.Add((_, builder) =>
+                {
+                    builder.AddHttpMessageHandler<BlazorClientHttpMessageHandler>();
+                });
+            });
+        }
+
         public override void ConfigureServices(ServiceConfigurationContext context)
         {
             var environment = context.Services.GetSingletonInstance<IWebAssemblyHostEnvironment>();

templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/Shared/LanguageSwitch.razor

@@ -0,0 +1,67 @@
+@using Volo.Abp.Localization
+@using System.Globalization
+@inject ILanguageProvider LanguageProvider
+@inject IJSRuntime JsRuntime
+@if (_languages != null && _languages.Count > 1)
+{
+    <Dropdown>
+        <DropdownToggle Color="Color.None">
+            @_currentLanguage.DisplayName
+        </DropdownToggle>
+        <DropdownMenu>
+            @foreach (var language in _languages)
+            {
+                if (language == _currentLanguage)
+                {
+                    continue;
+                }
+
+                <DropdownItem Clicked="() => ChangeLanguageAsync(language)">@language.DisplayName</DropdownItem>
+            }
+        </DropdownMenu>
+    </Dropdown>
+}
+@code {
+    private IReadOnlyList<LanguageInfo> _languages;
+    private LanguageInfo _currentLanguage;
+
+    protected override async Task OnInitializedAsync()
+    {
+        var selectedLanguageName = await JsRuntime.InvokeAsync<string>(
+            "localStorage.getItem",
+            "Abp.SelectedLanguage"
+            );
+
+        _languages = await LanguageProvider.GetLanguagesAsync();
+
+        if (!_languages.Any())
+        {
+            return;
+        }
+
+        if (!selectedLanguageName.IsNullOrWhiteSpace())
+        {
+            _currentLanguage = _languages.FirstOrDefault(l => l.UiCultureName == selectedLanguageName);
+        }
+
+        if (_currentLanguage == null)
+        {
+            _currentLanguage = _languages.FirstOrDefault(l => l.UiCultureName == CultureInfo.CurrentUICulture.Name);
+        }
+
+        if (_currentLanguage == null)
+        {
+            _currentLanguage = _languages.FirstOrDefault();
+        }
+    }
+
+    private async Task ChangeLanguageAsync(LanguageInfo language)
+    {
+        await JsRuntime.InvokeVoidAsync(
+            "localStorage.setItem",
+            "Abp.SelectedLanguage", language.UiCultureName
+            );
+
+        await JsRuntime.InvokeVoidAsync("location.reload");
+    }
+}

templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/Shared/MainLayout.razor

@@ -6,7 +6,8 @@
 
 <div class="main">
     <div class="top-row px-4 auth">
-        <LoginDisplay />
+        <LanguageSwitch/>
+        <LoginDisplay/>
         <a href="https://docs.microsoft.com/aspnet/" target="_blank">About</a>
     </div>