错误：“System.InvalidOperationException：无法找到所需的服务”。怎么修？

Question

运行代码时出现此错误

 Application startup exception
System.InvalidOperationException: Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddControllers' inside the call to 'ConfigureServices(...)' in the application startup code.
   at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.EnsureControllerServices(IEndpointRouteBuilder endpoints)
   at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.MapControllers(IEndpointRouteBuilder endpoints)
   at API.Startup.<>c.<Configure>b__7_0(IEndpointRouteBuilder endpoints) in /Users/fathindosunmu/OneDrive/MyProjects/GitHubProjects/Reactivities/Reactivities/WebAPI/Startup.cs:line 168
   at Microsoft.AspNetCore.Builder.EndpointRoutingApplicationBuilderExtensions.UseEndpoints(IApplicationBuilder builder, Action`1 configure)
   at API.Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in /Users/fathindosunmu/OneDrive/MyProjects/GitHubProjects/Reactivities/Reactivities/WebAPI/Startup.cs:line 166
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.<Build>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
Unhandled exception. System.InvalidOperationException: Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddControllers' inside the call to 'ConfigureServices(...)' in the application startup code.
   at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.EnsureControllerServices(IEndpointRouteBuilder endpoints)
   at Microsoft.AspNetCore.Builder.ControllerEndpointRouteBuilderExtensions.MapControllers(IEndpointRouteBuilder endpoints)
   at API.Startup.<>c.<Configure>b__7_0(IEndpointRouteBuilder endpoints) in /Users/fathindosunmu/OneDrive/MyProjects/GitHubProjects/Reactivities/Reactivities/WebAPI/Startup.cs:line 168
   at Microsoft.AspNetCore.Builder.EndpointRoutingApplicationBuilderExtensions.UseEndpoints(IApplicationBuilder builder, Action`1 configure)
   at API.Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in /Users/fathindosunmu/OneDrive/MyProjects/GitHubProjects/Reactivities/Reactivities/WebAPI/Startup.cs:line 166
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.<Build>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
   at Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken)

虽然这是我的ConfigureServices 方法。

public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            services.AddDbContext<AppDbContext>(options =>
            {
                options.UseLazyLoadingProxies();
                options.UseSqlServer(
                    Configuration.GetConnectionString("MsSqlConnection"));
            });
            
            services.AddCors(options =>
            {
                options.AddPolicy("CorsAllowAll",
                    builder =>
                    {
                        builder.WithOrigins("http://localhost:3000");
                        builder.WithExposedHeaders("WWW-Authenticate");
                        builder.AllowAnyHeader();
                        builder.AllowAnyMethod();
                        builder.AllowCredentials();
                    });
            });

            services.AddMediatR(typeof(List.Handler).Assembly);
            services.AddAutoMapper(typeof(List.Handler));
            services.AddSignalR();
            services.AddMvc(options =>
            {
                var policy = new AuthorizationPolicyBuilder().RequireAuthenticatedUser().Build();
                options.Filters.Add(new AuthorizeFilter(policy));
                
            }).AddFluentValidation(config=> 
                config.RegisterValidatorsFromAssemblyContaining<Create>());
            
            
            var builder = services.AddIdentityCore<AppUser>();
            var identityBuilder = new IdentityBuilder(builder.UserType, builder.Services);
            identityBuilder.AddEntityFrameworkStores<AppDbContext>();
            identityBuilder.AddSignInManager<SignInManager<AppUser>>();

            services.AddAuthorization(options =>
            {
                options.AddPolicy("IsActivityHost", policy =>
                {
                    policy.Requirements.Add(new IsHostRequirement());
                });
            });
            services.AddTransient<IAuthorizationHandler, IsHostRequirementHandler>();

            
            var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["JWT:SigningKey"]));
            services.AddAuthorization();
            services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).
                AddJwtBearer(options =>
                {
                    options.TokenValidationParameters = new TokenValidationParameters
                    {
                        ValidateIssuerSigningKey = true,
                        IssuerSigningKey = key,
                        ValidateAudience= false,
                        ValidateIssuer = false,
                        ValidateLifetime = true,
                        ClockSkew = TimeSpan.Zero
                    };
                    options.Events = new JwtBearerEvents
                    {
                        OnMessageReceived = context =>
                        {
                            //receiving jwt token as a request header from client because the chatHub is not a HTTP request
                            //Protocol
                            var accessToken = context.Request.Query["access_token"];
                            var path = context.HttpContext.Request.Path;
                            if (!string.IsNullOrEmpty(accessToken) && (path.StartsWithSegments("/chat")))
                            {
                                context.Token = accessToken;
                            }

                            return Task.CompletedTask;
                        }
                    };
                });
            services.AddScoped<IJWTGenerator, JWTGenerator>();
            services.AddScoped<IUserAccessor, UserAccessor>();
            services.AddScoped<IPhotoAccessor, PhotoAccessor>();
            services.AddScoped<IProfileReader, ProfileReader>();
            services.Configure<CloudinarySettings>(Configuration.GetSection("Cloudinary"));
        }

另外，program.cs 包含这个

public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }

为什么添加了所需的服务后此错误仍然存​​在？我该如何解决？

Answer 1

当服务MvcMarkerService 缺失时，EnsureControllerServices 抛出异常。当您调用 .UseEndpoints 时，这会在您的 Startup.Configure 方法中发生。

在ConfigureServices 中，您调用.AddMvc，所以我不确定为什么会抛出异常。但是，在 .NET Core 3.1 中创建 MVC Web 应用程序时，建议调用 .AddControllersWithViews 或 one of the other ways to register the MVC services。您在Startup.ConfigureServices 中注册服务和在Startup.Configure 中配置管道的方式存在问题，您需要解决。