Localizing Blazor WASM applications with a language picker

This article presents code how to localize a Blazor WASM app with a language picker. This is part of globalizing an app. The sample app is in this sample app in GitHub: https://github.com/toreaurstadboss/HelloBlazorLocalization

First off, we need to add some Nuget package references, such as adding a capability of using local storage in a convenient way in the Blazor WASM app. The project file of the sample app has this setup :

Project file - HelloBlazorLocalization.csproj
<Project Sdk="Microsoft.NET.Sdk.BlazorWebAssembly">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
	<BlazorWebAssemblyLoadAllGlobalizationData>true</BlazorWebAssemblyLoadAllGlobalizationData>
  </PropertyGroup>

  <ItemGroup>
    <Compile Remove="Shared\Resources\**" />
    <Content Remove="Shared\Resources\**" />
    <EmbeddedResource Remove="Shared\Resources\**" />
    <None Remove="Shared\Resources\**" />
  </ItemGroup>

  <ItemGroup>
	  <PackageReference Include="Blazored.LocalStorage" Version="4.3.0" />
	  <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="6.0.3" />
	  <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="6.0.3" PrivateAssets="all" />
	  <PackageReference Include="Microsoft.AspNetCore.Localization" Version="2.1.1" />
	  <PackageReference Include="Microsoft.AspNetCore.WebUtilities" Version="2.2.0" />
	  <PackageReference Include="Microsoft.Extensions.Localization" Version="6.0.3" />
  </ItemGroup>

  <ItemGroup>
    <Folder Include="wwwroot\flag-icons\" />
  </ItemGroup>

  <ItemGroup>
    <None Include="HelloBlazorLocalization.sln" />
  </ItemGroup>

</Project>

Note the use of the property setting : BlazorWebAssemblyLoadAllGlobalizationData This is required to add localization to your Blazor WASM app ! Also note that we use Blazored.LocalStorage to write and access local storage. Let's look at the Program.cs file next how we set up the app.

Program.cs

using Blazored.LocalStorage;
using HelloBlazorLocalization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

builder.Services.Configure<RequestLocalizationOptions>(options =>
{
    string[] supportedCultures = new[] { "no", "en" };
    options
        .AddSupportedCultures(supportedCultures)
        .AddSupportedUICultures(supportedCultures)
        .SetDefaultCulture("no");
});

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

builder.Services.AddBlazoredLocalStorage();

await builder.Services.BuildServiceProvider().SetDefaultCultureAsync();

await builder.Build().RunAsync();

An extension method is added to ServiceProvider to load up selected culture from local storage. It also inspects the query string set, if any, since language picker component presented later on will reload the Blazor WASM app after selecting language.

WebAssemblyHostExtensions.cs

using Blazored.LocalStorage;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
using Microsoft.AspNetCore.WebUtilities;
using System.Globalization;

namespace HelloBlazorLocalization
{

    public static class WebAssemblyHostExtensions
    {
        public async static Task SetDefaultCultureAsync(this ServiceProvider serviceProvider)
        {
            var navigationManager = serviceProvider.GetService<NavigationManager>(); 
            var uri = navigationManager!.ToAbsoluteUri(navigationManager.Uri);
            var queryStrings = QueryHelpers.ParseQuery(uri.Query);
            var localStorage = serviceProvider.GetRequiredService<ILocalStorageService>();

            if (queryStrings.TryGetValue("culture", out var selectedCulture))
            {
                await localStorage.SetItemAsStringAsync("culture", selectedCulture);
            }

            var cultureString = await localStorage.GetItemAsync<string>("culture");
            CultureInfo cultureInfo;

            if (!string.IsNullOrWhiteSpace(cultureString))
            {
                cultureInfo = new CultureInfo(cultureString);
            }
            else
            {
                cultureInfo = new CultureInfo("en-US");
            }

            CultureInfo.DefaultThreadCurrentCulture = cultureInfo;
            CultureInfo.DefaultThreadCurrentUICulture = cultureInfo;
        }
    }

}

Now, let's look at the Index.razor file where we repeat some of the code in the extension method shown above.

Index.razor

@page "/"
@using System.Globalization;

@inject NavigationManager NavigationManager
@inject Blazored.LocalStorage.ILocalStorageService LocalStorage
@inject IStringLocalizer<SharedResources> Localizer

<PageTitle>@Localizer["Home"]</PageTitle>

<h1>@Localizer["Home"]</h1>

@Localizer["HomeDescription"]

<SurveyPrompt Title="How is Blazor working for you?" />


@code {

    protected override async Task OnParametersSetAsync()
    {
        var uri = NavigationManager.ToAbsoluteUri(NavigationManager.Uri);
        var queryStrings = QueryHelpers.ParseQuery(uri.Query);
        if (queryStrings.TryGetValue("culture", out var selectedCulture))
        {
            await LocalStorage.SetItemAsStringAsync("culture", selectedCulture);

        }
        else
        {
            selectedCulture = await LocalStorage.GetItemAsStringAsync("culture");
        }
        if (!string.IsNullOrWhiteSpace(selectedCulture))
        {
            var cultureInfo = new CultureInfo(selectedCulture);
            CultureInfo.DefaultThreadCurrentCulture = cultureInfo;
            CultureInfo.DefaultThreadCurrentUICulture = cultureInfo;            
        }

    }

}

To localize strings, we first do an inject of the IStringLocalizer as shown in the razor file. We also set the resource key when we fetch the localized text (Value). This is set up in the SharedResource files. This is done in the sample app in three files.

• An empty class called SharedResources at the root level
• Two resources files (.resx) called SharedResources.en.resx and SharedResources.no.resx

You can have multiple resource file in Blazor WASM. Note that we in Program.cs set up the ResourcesPath to the sub folder Resources, where we put the .resx files. See the sample app for details (clone the Github repo). Next up, let's look at the LanguagePicker.razor file that will show a language picker. The sample app got flag icons for all flags of countries so check out the folder flag-icons under wwwroot folder in the sample app.

LanguagePicker.razor

@using Microsoft.AspNetCore.Localization
@using Microsoft.Extensions.Options
@using System.Globalization
@inject IOptions<RequestLocalizationOptions> LocalizationOptions
@inject Blazored.LocalStorage.ILocalStorageService LocalStorage

<div class="mt-3 mb-3 mx-5">

    @foreach (var culture in LocalizationOptions.Value.SupportedCultures)
    { 
        
        <a style="cursor:pointer" onclick="location.href = '/?culture=@culture.ToString()';" class="text-decoration-none">
            <img style="width:20px" src="flag-icons/@(culture.Name).png" alt="@culture.Name" />
            <span class="badge rounded-pill mx-1 border border-primary 
            @((culture.ToString() == CultureInfo.CurrentCulture.ToString() || culture.ToString() == _selectedCulture) ?
                "btn btn-success" : "btn btn-info text-dark")">@culture</span>
        </a>  <br />
    }
</div>

@code {
    private string? _selectedCulture;
    protected override async Task OnParametersSetAsync()
    {
        _selectedCulture = await LocalStorage.GetItemAsStringAsync("culture");
    }
}

Note that Blazor WASM app should refresh entirely after choosing another language. Also note that you should set up multiple languages in your browser to get the expected results. You should have the supported languages set up in Blazor WASM, however it might still work to get the localization done if the language settings are not set up to include the specified languages. But if you do not see the expected results, check the language settings in your browser. And as can be seen, we use local storage to persist our selected language. The selected language is displayed with the green button to indicate selected. When the Blazor WASM reloads, the selected language is fetched from local storage. This can be seen in Application => Local Storage in F12 Developer Tools in Chrome for example, when running the app. Blazor WASM supports a reduced set of localization functionality, compared to Blazor server side apps.

A limited set of ASP.NET Core's localization features are supported:

✔️Supported: IStringLocalizer and IStringLocalizer are supported in Blazor apps.

❌Not supported: IHtmlLocalizer, IViewLocalizer, and Data Annotations localization are ASP.NET Core MVC features and not supported in Blazor apps.

Mocking Http Client used for Blazor apps using bUnit

This article will look at running http client calls used by Blazor apps using bUnit. First off, bUnit is a library to perform unit tests for Blazor apps. We will look at mocking http client calls in this article. I have added a Github repo with the sample code in this article here :

https://github.com/toreaurstadboss/BlazorHttpClientMocking
Setting up the project Nuget package references of the test project - BlazorHttpClientMocking.Test

 

    <PackageReference Include="bunit" Version="1.21.9" />
    <PackageReference Include="FluentAssertions" Version="6.11.0" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
    <PackageReference Include="Moq" Version="4.18.4" />
    <PackageReference Include="RichardSzalay.MockHttp" Version="6.0.0" />
    <PackageReference Include="xunit" Version="2.4.2" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="coverlet.collector" Version="3.2.0">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
 
 

We will use the Nuget package RichardSzalay.MockHttp to do much of the mocking of http client. The following helper extension methods allow us to easier add mocking of http client calls.

 
 
Helper extension methods for http client using bUnit - MockHttpClientBunitHelpers.cs
 
using Bunit;
using Microsoft.Extensions.DependencyInjection;
using RichardSzalay.MockHttp;
using System.Net;
using System.Net.Http.Headers;
using System.Text.Json;

namespace BlazorHttpClientMocking.Test.Helpers
{
    public static class MockHttpClientBunitHelpers
    {

        public static MockHttpMessageHandler AddMockHttpClient(this TestServiceProvider services, string baseAddress = @"http://localhost")
        {
            var mockHttpHandler = new MockHttpMessageHandler();
            var httpClient = mockHttpHandler.ToHttpClient();
            httpClient.BaseAddress = new Uri(baseAddress);
            services.AddSingleton<HttpClient>(httpClient);
            return mockHttpHandler;
        }

        public static T? FromResponse<T>(this HttpResponseMessage? response, JsonSerializerOptions? options = null)
        {
            if (response == null)
            {
                return default(T);
            }
            if (options == null)
            {
                options = new JsonSerializerOptions
                {
                    PropertyNameCaseInsensitive = true
                };
            }
            string responseString = response.Content.ReadAsStringAsync().Result;
            var result = JsonSerializer.Deserialize<T>(responseString, options);
            return result;
        }

        public static async Task<T?> FromResponseAsync<T>(this HttpResponseMessage? response, JsonSerializerOptions? options = null)
        {
            if (response == null)
            {
                return await Task.FromResult(default(T));
            }
            if (options == null)
            {
                options = new JsonSerializerOptions
                {
                    PropertyNameCaseInsensitive = true
                };
            }
            string responseString = await response.Content.ReadAsStringAsync();
            var result = JsonSerializer.Deserialize<T>(responseString, options);
            return result;
        }

        public static MockedRequest RespondJson<T>(this MockedRequest request, T content)
        {
            request.Respond(req =>
            {
                var response = new HttpResponseMessage(HttpStatusCode.OK);
                response.Content = new StringContent(JsonSerializer.Serialize(content));
                response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
                return response;
            });
            return request;
        }

        public static MockedRequest RespondJson<T>(this MockedRequest request, Func<T> contentProvider)
        {
            request.Respond(req =>
            {
                var response = new HttpResponseMessage(HttpStatusCode.OK);
                response.Content = new StringContent(JsonSerializer.Serialize(contentProvider()));
                response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
                return response;
            });
            return request;
        }


    }
}

 
 

The method AddMockHttpClient, which is an extension method on TestServiceProvider adds the mocked client. In the code above we read the response into a string and deserialize with System.Text.Json, defaulting to case insensitive property naming, since this is default System.Text.Json on web, but not elsewhere, such as in test projects.

Helper methods for serialization - SerializationHelpers.cs
  
using System.Text.Json;

namespace BlazorHttpClientMocking.Test.Helpers
{
    public static class SerializationHelpers
    {

        public static async Task<T?> DeserializeJsonAsync<T>(string path, JsonSerializerOptions? options = null)
        {
            if (options == null)
            {
                options = new JsonSerializerOptions
                {
                    WriteIndented = true,
                    IncludeFields = true,
                    PropertyNameCaseInsensitive = true
                };
            }

            using (Stream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                if (File.Exists(path) && stream.Length > 0)
                {
                    T? obj = await JsonSerializer.DeserializeAsync<T>(stream, options);
                    return obj;
                }
                return default(T);
            }

        }

    }
}

  

Let's look at a unit test which then sets up a mocked http client response that is used in the Blazor sample app on the FetchData page.

using BlazorHttpClientMocking.Test.Helpers;
using Bunit;
using FluentAssertions;
using Microsoft.Extensions.DependencyInjection;
using RichardSzalay.MockHttp;
using static BlazorHttpClientMocking.Pages.FetchData;

namespace BlazorHttpClientMocking.Test
{
    public class FetchDataTests
    {
        [Fact]
        public async Task FetchData_HttpClient_Request_SuccessResponse()
        {
            //Arrange 
            using var ctx = new TestContext();
            var httpMock = ctx.Services.AddMockHttpClient();
            string knownUrl = @"/sample-data/weather.json";
            var sampleData = await SerializationHelpers.DeserializeJsonAsync<WeatherForecast[]>(knownUrl.TrimStart('/')); //trimming start of url since we need a physical path
            httpMock.When(knownUrl).RespondJson(sampleData);

            //Act
            var httpClient = ctx.Services.BuildServiceProvider().GetService<HttpClient>();
            var httpClientResponse = await httpClient!.GetAsync(knownUrl);
            httpClientResponse.EnsureSuccessStatusCode();
            var forecasts = await httpClientResponse.FromResponseAsync<WeatherForecast[]>();

            //Assert 
            forecasts.Should().NotBeNull();
            forecasts.Should().HaveCount(5);
        }

    }
}

In the arrange part of the unit test above, we create a TestContext and add a mocked http client using the extension method shown earlier. We read out the sample json data and set up using the When method and remember to add "/" to the path as this is expected since we have a baseAddress specified on the http client, set to @"http://localhost" default.

We retrieve http client via the Services collection on the TestContext and call BuildServiceProvider and GetService method to get the http client with the mocking. The mocking must be done via the When method and then we get the client. The mocked http client is a singleton service here.

We can also do parameters in the mocking of http client calls.

Using parameters in http client calls

Lets first add parameter support for the Fetchdata razor page. Fetchdata.razor

 @page "/fetchdata/"
 @page "/fetchdata/{id:int}"
 
  
 
 @code {
    internal WeatherForecast[]? forecasts;

    [Parameter]
    public int? Id { get; set; }

    protected override async Task OnInitializedAsync()
    {
        forecasts = await Http.GetFromJsonAsync<WeatherForecast[]>($"sample-data/weather.json");
        if (forecasts != null && Id >= 0 && Id < 5)
        {
            forecasts = forecasts.Skip(Id.Value).Take(1).ToArray();
        }
    }

    public class WeatherForecast
    {
        public DateOnly Date { get; set; }

        public int TemperatureC { get; set; }

        public string? Summary { get; set; }

        public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
    }
}
 

Let's now look at using parameters in mocked http client calls in another unit test.

 
 
         [Fact]
        public async Task FetchData_HttpClient_With_Parameter_Request_SuccessResponse()
        {
            //Arrange 
            using var ctx = new TestContext();
            var httpMock = ctx.Services.AddMockHttpClient();
            string knownUrl = @"/sample-data/weather.json/0";
            string fileUrl = @"sample-data/weather.json";

            var sampleData = await SerializationHelpers.DeserializeJsonAsync<WeatherForecast[]>(fileUrl); //trimming start of url since we need a physical path
            httpMock.When(knownUrl).RespondJson(sampleData);

            //Act
            var renderComponent = ctx.RenderComponent<FetchData>(p => p
                .Add(fd => fd.Id, 0));

            //Assert 
            renderComponent.Instance.forecasts.Should().NotBeNull();

            renderComponent.Instance.forecasts.Should().HaveCount(1);    
        }
    
 
 

Here we use bUnit's capabilities in rendering Blazor components using the RenderComponent method and we also set the Id parameter here to the value 0 which now will prepare our component with the right forecasts, here only one forecast will be shown. We use the Instance property to look at the forecasts field of the component. internal WeatherForecast[]? forecasts; So bUnit can be used both the mock http client calls and also render Blazor components and also support parametrized calls of mocked http client calls.


Finally a tip concerning letting your internal fields to be available for test project. In the csproj file of the application we can set it up like in this example :

  <ItemGroup>
		<AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
			<_Parameter1>BlazorHttpClientMocking.Test</_Parameter1>
		</AssemblyAttribute>
  </ItemGroup>

Here we set up that the test project can see the internals of the blazor app project. This allows the test project to see internal methods and internal fields, internal classes and so on. This allows you to avoid changing parameters or fields in your components from private to public for example and instead change access modifier to internal so the tests can access those members.

Writing cookies with Blazor WASM

This article presents some source code of how to write and read cookies from Blazor WebAssembly - WASM. For Blazor WASM, we are going to use Javascript to write these cookies. Blazor WASM has not an easy way to write these cookies programatically, as the use of HttpContext accessor is discouraged and not available, i.e. you cannot just add cookies without round trips to backend services.

But via Js, the client can write cookies. I looked into a helper lib to write such cookies and do so using different attribute values for the cookies.
The following Mozilla Developer Network (MDN) page is helpful in detailing cookies, which attribute values can be set on them. Cookies are used to give user experience since they track user's on a web site and give tailored user experience - and advertising - and also can track the users accross servers / web sites as third-party cookies. They are small string values that are either stored on clients inside cookie storage in the browser's folder on the user's hard drive or in memory or other place such as partitioned cookies.

MND page - document.cookies

https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie First off, the source code is here:

Forked Repo with adaptions in cookie handling for Blazor WASM

https://github.com/toreaurstadboss/AltairCA.Blazor.WebAssembly.Cookie This is a forked repo from this repo:

Original repo with cookie handling for Blazor WASM

https://github.com/AltairCA/AltairCA.Blazor.WebAssembly.Cookie The most recent branch of mine is this one: https://github.com/toreaurstadboss/AltairCA.Blazor.WebAssembly.Cookie/blob/feature/more-cookie-keys/README.md
Let's first look at the interface for the util class that will write cookies :

Interface for cookie handling for Blazor.wasm, IAltairCABlazorCookieUtil.cs

 
 
using AltairCA.Blazor.WebAssembly.Cookie.Models;

namespace AltairCA.Blazor.WebAssembly.Cookie
{
    public interface IAltairCABlazorCookieUtil
    {
        /// <summary>
        /// Set a object in the cookie
        /// </summary>
        /// <param name="key">The key for the cookie (name)</param>
        /// <param name="value">Cookie value</param>
        /// <param name="span">TimeSpan that will be set to the 'expires' attribute value</param>
        /// <param name="path">Path in the request url which must exist for the cookie to be sent in requests </param>
        /// <param name="domain">The host to which the cookie will be sent</param>
        /// <param name="secure">Specifies that the cookie will be sent only over secure protocols</param>
        /// <param name="isSession">Flags the cookie as a session cookie (temporal) by setting the 'expires' attribute value to ''</param>
        /// <param name="partitioned">Requires that the browser has activated partitioned cookies</param>
        /// <param name="maxAgeInSeconds">Maximum age in seconds</param> 
        /// <returns></returns>
        Task SetValueAsync(string key, object value, TimeSpan? span = null, string? path = null,
            string? domain = null, bool? secure = null, SameSite? sameSite = null, bool? partitioned = null, 
            bool? isSession = null, int? maxAgeInSeconds = null);

        /// <summary>
        /// Set a string in the cookie
        /// </summary>
        /// <param name="key">The key for the cookie (name)</param>
        /// <param name="value">Cookie value</param>
        /// <param name="span">TimeSpan that will be set to the 'expires' attribute value</param>
        /// <param name="path">Path in the request url which must exist for the cookie to be sent in requests </param>
        /// <param name="domain">The host to which the cookie will be sent</param>
        /// <param name="secure">Specifies that the cookie will be sent only over secure protocols</param>
        /// <param name="isSession">Flags the cookie as a session cookie (temporal) by setting the 'expires' attribute value to ''</param>
        /// <param name="partitioned">Requires that the browser has activated partitioned cookies</param>
        /// <param name="maxAgeInSeconds">Maximum age in seconds</param> 
        /// <returns></returns>
        Task SetValueAsync(string key, string value, TimeSpan? span = null, string? path=null, string? domain=null, 
            bool? secure = null, SameSite? sameSite = null, bool? partitioned = null, bool? isSession = null,
            int? maxAgeInSeconds = null);
       
        Task<string> GetValueAsync(string key);
       
        Task<T> GetValueAsync<T>(string key) where T : class;
        
        Task RemoveAsync(string key, string? path = null);

    }
}
 
 

And here is the implementation.

Implementation for cookie handling for Blazor.wasm, AltairCABlazorCookieUtil.cs

 
 
using System.ComponentModel;
using AltairCA.Blazor.WebAssembly.Cookie.Models;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.JSInterop;
using Newtonsoft.Json;

namespace AltairCA.Blazor.WebAssembly.Cookie
{

    internal class AltairCABlazorCookieUtil : IAltairCABlazorCookieUtil
    {
        readonly IJSRuntime JSRuntime;
        private readonly AltairCABlazorCookieConfigOptions _settings;
        public AltairCABlazorCookieUtil(IJSRuntime jsRuntime,IOptions<AltairCABlazorCookieConfigOptions> options)
        {
            JSRuntime = jsRuntime;
            _settings = options.Value;
        }

        public Task SetValueAsync(string key, object value, TimeSpan? span = null, string? path = null,
            string? domain = null, bool? secure = null, SameSite? sameSite = null, bool? partitioned = null, bool? isSession = null,
            int? maxAgeInSeconds = null)
        {
            return SetValueAsync(key, JsonConvert.SerializeObject(value), span, path, domain, secure, sameSite, partitioned,
                isSession);
        }
        public async Task SetValueAsync(string key, string value, TimeSpan? span = null, string? path=null, string? domain=null, 
            bool? secure = null, SameSite? sameSite = null, bool? partitioned = null, bool? isSession = null,
             int? maxAgeInSeconds = null)
        {
            if (string.IsNullOrWhiteSpace(path))
                path = _settings.Path;
            if (!span.HasValue)
                span = _settings.DefaultExpire;
            if (string.IsNullOrWhiteSpace(domain))
                domain = _settings.Domain;
            if (!secure.HasValue)
                secure = _settings.IsSecure;
            
            var curExp = span.HasValue && span.Value.Ticks > 0 && isSession != true && !maxAgeInSeconds.HasValue ?  DateToUTC(span.Value) : "";            
            
            List<string> keyvals = new List<string>();
            keyvals.Add($"{key}={value}");
            keyvals.Add($"expires={curExp}");
            keyvals.Add($"path={path}");
            if(!string.IsNullOrWhiteSpace(domain))
                keyvals.Add($"domain={domain}");
            if(secure.HasValue && secure.Value)
                keyvals.Add("secure");
            if (maxAgeInSeconds.HasValue && isSession != true)
            {
                keyvals.Add($"max-age={maxAgeInSeconds.Value}");
            }
            if (sameSite.HasValue){
                DescriptionAttribute desc = (DescriptionAttribute) typeof(SameSite).GetMember(sameSite.Value.ToString()).First().GetCustomAttributes(typeof(DescriptionAttribute), false).First();
                keyvals.Add($"samesite={desc.Description}");
            } 
            string cookieToSet = string.Join(";", keyvals);
            if (partitioned == true){
                cookieToSet += ";partitioned";
            }
            
            await SetCookie(cookieToSet);
        }

        public async Task RemoveAsync(string key,string path = null)
        {
            if (string.IsNullOrWhiteSpace(path))
                path = _settings.Path;
            List<string> keyvals = new List<string>();
            keyvals.Add($"{key}=");
            keyvals.Add($"Path={path}");
            keyvals.Add($"expires=Thu, 01 Jan 1970 00:00:01 GMT;");
            await SetCookie(string.Join(";", keyvals));
        }

        public async Task<T> GetValueAsync<T>(string key) where T : class
        {
            var res = await GetValueAsync(key);
            if (res == null)
                return default(T);
            return JsonConvert.DeserializeObject<T>(res);
        }
        public async Task<string> GetValueAsync(string key)
        {
            var cValue = await GetCookie();
            if (string.IsNullOrEmpty(cValue)) return null;                

            var vals = cValue.Split(';');
            foreach (var val in vals)
                if(!string.IsNullOrEmpty(val) && val.IndexOf('=') > 0)
                    if(val.Substring(0, val.IndexOf('=')).Trim().Equals(key, StringComparison.OrdinalIgnoreCase))
                        return val.Substring(val.IndexOf('=') + 1);
            return null;
        }

        private async Task SetCookie(string value)
        {
            await JSRuntime.InvokeVoidAsync("eval", $"document.cookie = \'{value}\'");
        }

        private async Task<string> GetCookie()
        {
            return await JSRuntime.InvokeAsync<string>("eval", $"document.cookie");
        }
        private static string DateToUTC(TimeSpan span) => DateTime.Now.Add(span).ToUniversalTime().ToString("R");
    }
}


//we also have this enum used in cookie handler class above

using System.ComponentModel;

namespace AltairCA.Blazor.WebAssembly.Cookie.Models;

public enum SameSite {
    
    [Description("lax")]
    Lax = 0,

    [Description("strict")]
    Strict = 1,

    [Description("none")]
    None = 2
    
}
 
 

The MDN article details a lot around cookies and there are a lot of way of controlling these cookies via attributes. Most browsers limit Cookie sizes to be 4 kilobytes maximum length (4096 bytes) of all cookies on a server. And a maxiumum of 50 cookies, still must be below the 4 kB limit. https://stackoverflow.com/a/4604212 We set up the cookie handling via Program.cs of a Blazor WASM like this :

Implementation for cookie handling for Blazor.wasm, AltairCABlazorCookieUtil.cs

 

builder.Services.AddAltairCACookieService(options =>
{
    options.DefaultExpire = TimeSpan.FromMinutes(15);
});

This extension method on IServiceCollection adds the cookie handling as a singleton service, AltairCABlazorCookieUtil.cs

 

using AltairCA.Blazor.WebAssembly.Cookie.Models;
using Microsoft.Extensions.DependencyInjection;

namespace AltairCA.Blazor.WebAssembly.Cookie.Framework;

public static class PipelineExtension
{
    public static IServiceCollection AddAltairCACookieService(this IServiceCollection services,Action<AltairCABlazorCookieConfigOptions> configure)
    {
        services.Configure(configure);
        services.AddSingleton<IAltairCABlazorCookieUtil, AltairCABlazorCookieUtil>();
        return services;
    } 
}

//note - the extension method above also uses this model class to set up default options for cookies 

namespace AltairCA.Blazor.WebAssembly.Cookie.Models;

public class AltairCABlazorCookieConfigOptions
{
    public TimeSpan DefaultExpire { get; set; } = TimeSpan.Zero;
    public string Path { get; set; } = "/";
    public string Domain { get; set; } = string.Empty;
    public bool IsSecure { get; set; } = false;
}

As can be seen in the implementation, these default config options are injected in the constructor via :

AltairCABlazorCookieUtil.cs - constructor parameter injecting the options which was set via services.Configure in the extension method of the pipeline

 
public AltairCABlazorCookieUtil(IJSRuntime jsRuntime,IOptions<AltairCABlazorCookieConfigOptions> options)
{
	JSRuntime = jsRuntime;
    _settings = options.Value;
}

As we can see, we remove the cookie by setting it to expire at Unix Epoch zero (1970, 1st of January) in the cookie handling. A good util to inspect Cookies and even edit them are available in this Google plugin: Edit this Cookie

Counter.razor - using the Cookie util in Blazor WASM sample app

 
 
 @inject IAltairCABlazorCookieUtil _cookieUtil;
 
  
 
 
private async Task IncrementCount()
    {
        currentCount++;
        Content = await _cookieUtil.GetValueAsync("c");
        ContentObj = await _cookieUtil.GetValueAsync<object>("d");

        await _cookieUtil.SetValueAsync("c", "this is cookie with key c");
        await _cookieUtil.SetValueAsync("d", new
        {
            hello = "hello world. i am a cookie with key d"
        });
        await _cookieUtil.SetValueAsync("cookieWithSameSiteSet", "Cookie which specified cross site request inclusion of the cookie : SameSite value (lax | strict | none)", sameSite: SameSite.Lax);

        await _cookieUtil.SetValueAsync("cookiePartitioned", "Partitioned cookie", partitioned: true);
     
        await _cookieUtil.SetValueAsync("cookieWithMaxAge", "Max age cookie", maxAgeInSeconds: 600);

        await _cookieUtil.SetValueAsync("cookieWhichIsToBeSetToSessionCookie", "Session cookie = temporal cookie", isSession: true);

    }
  

One important note about the cookie util here, observe the usage of the 'eval' method to set the cookie via Js in the util class and also retrieve cookies :

Implementation for cookie handling for Blazor.wasm, AltairCABlazorCookieUtil.cs

 
 
   private async Task SetCookie(string value)
        {
            await JSRuntime.InvokeVoidAsync("eval", $"document.cookie = \'{value}\'");
        }

        private async Task<string> GetCookie()
        {
            return await JSRuntime.InvokeAsync<string>("eval", $"document.cookie");
        }
 
 

Using 'eval' we let Js run the Js code we pass in here in Blazor WASM app. This also means that we cannot write HttpOnly cookies, since we rely fully on Js here.

As some of you know, third party cookie support are planned by Chrome to be discontinued in support. The following article is interesting reading about this. https://itrust-digital.com/cookieless-future/