ASP.NET 核心 3：无法解析来自根提供商的作用域服务 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]'

Question

我在做运行项目的时候遇到了这个问题： （我用过asp.net core 3。）

Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider.

我该如何解决这个问题？

ApplicationDbContext class:

public class ApplicationDbContext : IdentityDbContext<User, Role, int, 
UserClaim, UserRole, UserLogin, RoleClaim, UserToken>
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
    {

    }
public static async Task CreateAdminAccount(IServiceProvider 
serviceProvider, IConfiguration configuration)
    {
        UserManager<User> userManager = 
serviceProvider.GetRequiredService<UserManager<User>>();
        RoleManager<Role> roleManager = 
serviceProvider.GetRequiredService<RoleManager<Role>>();

        string userName = configuration["Data:AdminUser:Name"];
        string email = configuration["Data:AdminUser:Email"];
        string password = configuration["Data:AdminUser:Password"];
        string role = configuration["Data:AdminUser:Role"];

        if (await userManager.FindByNameAsync(userName) == null)
        {
            if (await roleManager.FindByNameAsync(role) == null)
            {
                await roleManager.CreateAsync(new Role(role));
            }

            User user = new User
            {
                Email = email,
                UserName = userName
            };
            var result = userManager.CreateAsync(user, password);
            if (result.IsCompletedSuccessfully)
            {
                await userManager.AddToRoleAsync(user, role);
            }
        }
    }
}

错误详情：

An error occurred while starting the application. AggregateException: One or more errors occurred. (Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider.) System.Threading.Tasks.Task.ThrowIfExceptional(bool includeTaskCanceledExceptions)

InvalidOperationException: Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider. Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(Type serviceType, IServiceScope scope, IServiceScope rootScope)

AggregateException: One or more errors occurred. (Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider.) System.Threading.Tasks.Task.ThrowIfExceptional(bool includeTaskCanceledExceptions) System.Threading.Tasks.Task.Wait(int millisecondsTimeout, CancellationToken cancellationToken) System.Threading.Tasks.Task.Wait() Alpha.Web.App.Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in Startup.cs + ApplicationDbContext.CreateAdminAccount(app.ApplicationServices, Configuration).Wait(); System.RuntimeMethodHandle.InvokeMethod(object target, object[] arguments, Signature sig, bool constructor, bool wrapExceptions) System.Reflection.RuntimeMethodInfo.Invoke(object obj, BindingFlags invokeAttr, Binder binder, object[] parameters, CultureInfo culture) Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(object instance, IApplicationBuilder builder) Microsoft.AspNetCore.Hosting.ConfigureBuilder+<>c__DisplayClass4_0.b__0(IApplicationBuilder builder) Microsoft.AspNetCore.Hosting.GenericWebHostBuilder+<>c__DisplayClass13_0.b__2(IApplicationBuilder app) Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter+<>c__DisplayClass0_0.g__MiddlewareFilterBuilder|0(IApplicationBuilder builder) Microsoft.AspNetCore.Server.IIS.Core.IISServerSetupFilter+<>c__DisplayClass2_0.b__0(IApplicationBuilder app) Microsoft.AspNetCore.HostFilteringStartupFilter+<>c__DisplayClass0_0.b__0(IApplicationBuilder app) Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken) Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken) Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token) Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token) Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run(IHost host) Alpha.Web.App.Program.Main(string[] args) in Program.cs + CreateHostBuilder(args).Build().Run();

Show raw exception details InvalidOperationException: Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider. Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(Type serviceType, IServiceScope scope, IServiceScope rootScope) Microsoft.Extensions.DependencyInjection.ServiceProvider.Microsoft.Extensions.DependencyInjection.ServiceLookup.IServiceProviderEngineCallback.OnResolve(Type serviceType, IServiceScope scope) Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope) Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType) Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType) Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider) Alpha.DataAccess.ApplicationDbContext.CreateAdminAccount(IServiceProvider serviceProvider, IConfiguration configuration) in ApplicationDbContext.cs + UserManager userManager = serviceProvider.GetRequiredService>();

Show raw exception details System.InvalidOperationException: Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.UserManager`1[Alpha.Models.Identity.User]' from root provider. at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(Type serviceType, IServiceScope scope, IServiceScope rootScope) at Microsoft.Extensions.DependencyInjection.ServiceProvider.Microsoft.Extensions.DependencyInjection.ServiceLookup.IServiceProviderEngineCallback.OnResolve(Type serviceType, IServiceScope scope) at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider) at Alpha.DataAccess.ApplicationDbContext.CreateAdminAccount(IServiceProvider serviceProvider, IConfiguration configuration) in E:\Archives\Projects\Alpha\Alpha.DataAccess\ApplicationDbContext.cs:line 92 .NET Core 3.0.0 X64 v4.0.0.0 | Microsoft.AspNetCore.Hosting version 3.0.0-rc2.19465.2 | Microsoft Windows 10.0.17763 |
Need help?

Answer 1

从您提供的屏幕截图可以看出，您在 Startup.Configure 中有以下行：

ApplicationDbContext.CreateAdminAccount(app.ApplicationServices, Configuration)
    .Wait();

存储在 IApplicationBuilder.ApplicationServices 中的 IServiceProvider 实例是您应用程序的 root 服务提供者。错误消息指出它无法解析来自 root 服务提供商的 scoped 服务。

这个问题经常出现，但最简单的解决方案是将 IServiceProvider 注入 Configure 方法并将其传递给 CreateAdminAccount:

public void Configure(IApplicationBuilder app, IServiceProvider serviceProvider)
{
    ApplicationDbContext.CreateAdminAccount(serviceProvider, Configuration)
        .Wait();
}

传递给 Configure 的 IServiceProvider 实例是 scoped，这意味着您可以使用它来创建范围服务。

这就是完成这项工作所需的全部内容，但在 Program 中进行此类播种更为常见。这使得播种问题与配置管道分开，并且还允许使用 async/await。这是一个例子：

public class Program
{
    public static async Task Main(string[] args)
    {
        var host = CreateHostBuilder(args).Build();

        using (var scope = host.Services.CreateScope())
        {
            var serviceProvider = scope.ServiceProvider;
            var config = serviceProvider.GetRequiredService<IConfiguration>();

            await ApplicationDbContext.CreateAdminAccount(serviceProvider, config);
        }

        await host.RunAsync();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        // ...
}

您也可以解析 Main 中的 UserManager<User> 和 RoleManager<Role>，并将它们传递给 CreateAdminAccount 而不是让它使用服务定位器方法。