How to use a service directly in Startup.cs

Question

I'm trying to inject and use a service directly in Startup.cs in my Blazor application (MVVM). When I try to call a method from that service, I receive the same error message as when you failed to register the service properly:

I am doing this to read a value from the localstorage to set the language in startup.cs. for further information, see:
https://learn.microsoft.com/en-us/aspnet/core/blazor/globalization-localization?view=aspnetcore-6.0&pivots=server#dynamically-set-the-culture-by-user-preference-1

This is how I added the service in Startup.cs:

Injecting:

public class Startup
    {
        private IStorageService storageService;

        public Startup(IConfiguration configuration, IStorageService storageService)
        {
            this.storageService = storageService;
            Configuration = configuration;
        }
    
        public IConfiguration Configuration { get; }

RegisterLocation:

        /// <summary>
        /// This method gets called by the runtime. Use this method to add services to the container.
        /// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        /// </summary>
        /// <param name="services"></param>
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddScoped<IStorageService, StorageService>();

            var circuitRetentionPeriod = Configuration.GetValue("DisconnectedCircuitRetentionPeriodInMinutes", 3);

            services.AddRazorPages();
            services.AddServerSideBlazor()
                .AddCircuitOptions(a => a.DisconnectedCircuitRetentionPeriod = System.TimeSpan.FromMinutes(circuitRetentionPeriod))
                .AddHubOptions(hub => hub.MaximumReceiveMessageSize = 100 * 128 * 128); // 100 MB

            // Add basic logging functionality
            services.AddLogging(loggingBuilder =>
            {
                // Clear all potential logging providers
                loggingBuilder.ClearProviders();

                // Add NLog which will output the log to a log file
                loggingBuilder.AddNLog();

                // Log output to the Visual Studio Debug output
                loggingBuilder.AddDebug();
            });

            services.AddScoped<CircuitHandler>((sp) => new CircuitHandlerService(sp.GetRequiredService<ILogger<CircuitHandlerService>>(), sp.GetRequiredService<CircuitsCounterService>()));
            services.AddSingleton<CircuitsCounterService>();

            services.AddScoped<CorrelationProvider>();

            services.AddAppBaseBlazorServices();
            services.AddAppBaseApplicationServices();

            services.AddApplicationServices();
            services.AddBlazorServices();
            services.AddForeignServices();
        }

UseService:

        /// <summary>
        /// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        /// </summary>
        /// <param name="app"></param>
        /// <param name="env"></param>
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

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

            var language = storageService.Load<LanguageDTO>(StorageKeys.Language);

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapBlazorHub();
                endpoints.MapFallbackToPage("/_Host");
            });
        }
    }

Implementation of StorageService.Load()

        public StorageService(ILocalStorageService storage, ILogger<StorageService> logger)
        {
            this.logger = logger is null ? new NullLogger<StorageService>() : logger;

            this.storage = storage;
        }
    
        public async Task<T> Load<T>(string key)
            where T : class, new()
        {
            try
            {
                var jsonString = await storage.GetItemAsStringAsync(key);

                if (string.IsNullOrEmpty(jsonString))
                {
                    logger.LogTrace("Local storage item with key '{}' not found. Return new object.", key);
                    return new T();
                }

                if (!jsonString.StartsWith("{"))
                {
                    // No matter if the data is encrypted try to decrypt the value and swallow if the data was not encrypted
                    try { jsonString = StringCipher.Decrypt(jsonString, PASSPHRASE); }
                    catch (FormatException) { }
                }

                if (logger.IsEnabled(LogLevel.Trace))
                {
                    var jDoc = JsonDocument.Parse(jsonString, new JsonDocumentOptions { AllowTrailingCommas = true });
                    jsonString = System.Text.Json.JsonSerializer.Serialize(jDoc, new JsonSerializerOptions { WriteIndented = true });
                    logger.LogTrace("Load value from local storage with key '{key}': {jsonString}", key, jsonString);
                }

                // Deserialize the object
                var result = JsonConvert.DeserializeObject<T>(jsonString);

                if (result is null)
                    return new T();

                else
                    return result;

            }
            catch (JSDisconnectedException)
            {
                // This exception es expected when the application try to load something but the Blazor circuit is closed i.e. when the page is refreshed with f5
                return new T();
            }

I also tried to register the service at the top of ConfigureServices, in case the previous location is too late.

Furthermore, I already found out on the internet and ChatGPT, that this should be totally possible. But can't find out what I am doing wrong.

Answer 1

Your requirement is calling a service to get the language so that you can set it for your blazor app. Since the language is defined in a local storage, I'm afraid we can write a static method so that we can get the value directly in Startup.cs.

var language = StorageService.GetLanguage();

public class StorageService
{
    public static string GetLanguage()
    {
        return "en-us";
    }
}

If we need to dynamically set the culture by user preference, we need to follow this section. following the document and this is the test result.

Answer 2

You can try something like this ?

startup.cs

public class Startup
{
    public IConfiguration Configuration { get; }
    private  IMyService _myService;
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }
    public void ConfigureServices(IServiceCollection services)
    {

        services.AddControllers();
        services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", new OpenApiInfo { Title = "serviceInStartup", Version = "v1" });
        });
        services.AddSingleton<IMyService, MyService>();
        SetService();
    }
    public void SetService()
    {
        MyService myService = new MyService();
        _myService = myService;
    }
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        _myService.ReturnMeString();
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseSwagger();
            app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "serviceInStartup v1"));
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
        
    }
}

If your service injects other services:

public class Startup
{
    public IConfiguration Configuration { get; }
    private static IMyService _myService;
    public Startup(IConfiguration configuration )
    {
        Configuration = configuration;
    }
    public void ConfigureServices(IServiceCollection services)
    {

        services.AddControllers();
        services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", new OpenApiInfo { Title = "serviceInStartup", Version = "v1" });
        });
        services.AddSingleton<IMySecondService, MySecondService>();
        services.AddSingleton<IMyService, MyService>();
        SetService(services.BuildServiceProvider());
    }
    public void SetService(IServiceProvider provider)
    {
        var mySecondService = provider.GetService<IMySecondService>();
        MyService myService = new MyService(mySecondService);
        _myService = myService;
    }
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        _myService.ReturnMeString();
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseSwagger();
            app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "serviceInStartup v1"));
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
        
    }
}