ASP.NET Core 3：无法从根提供程序解析作用域服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'

Question

当我运行项目时，遇到此问题：（我用过asp.net core 3。）

无法从根提供者处解析作用域服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'。

我该如何解决这个问题？

ApplicationDbContext类：

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);
            }
        }
    }
}

错误的详细信息：

启动应用程序时发生错误。 AggregateException：发生一个或多个错误。 （无法解析范围服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'来自根提供商。）System.Threading.Tasks.Task.ThrowIfExceptional（布尔includeTaskCanceledExceptions）

InvalidOperationException：无法解析作用域服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'来自根提供商。Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution（TypeserviceType，IServiceScope范围，IServiceScope rootScope）

AggregateException：发生一个或多个错误。 （无法解决范围服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'来自根提供商。）System.Threading.Tasks.Task.ThrowIfExceptional（布尔includeTaskCanceledExceptions）System.Threading.Tasks.Task.Wait（int毫秒超时，CancelationToken取消（Token）System.Threading.Tasks.Task.Wait（）Alpha.Web.App.Startup.Configure（IApplicationBuilder应用，Startup.cs中的IWebHostEnvironment env）+ApplicationDbContext.CreateAdminAccount（app.ApplicationServices，配置）.Wait（）; System.RuntimeMethodHandle.InvokeMethod（对象目标，对象[]参数，签名sig，布尔构造函数，布尔wrapExceptions）System.Reflection.RuntimeMethodInfo.Invoke（对象obj，BindingFlags invokeAttr，活页夹活页夹，object []参数，CultureInfo文化）Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke（对象实例，IApplicationBuilder构建器）Microsoft.AspNetCore.Hosting.ConfigureBuilder + <> c__DisplayClass4_0.b__0（IApplicationBuilder建造者）Microsoft.AspNetCore.Hosting.GenericWebHostBuilder + <> c__DisplayClass13_0.b__2（IApplicationBuilder应用程式）Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter + <> c__DisplayClass0_0.g__MiddlewareFilterBuilder | 0（IApplicationBuilder建造者）Microsoft.AspNetCore.Server.IIS.Core.IISServerSetupFilter + <> c__DisplayClass2_0.b__0（IApplicationBuilder应用程式）Microsoft.AspNetCore.HostFilteringStartupFilter + <> c__DisplayClass0_0.b__0（IApplicationBuilder应用程式）Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync（CancellationTokencancelToken）Microsoft.Extensions.Hosting.Internal.Host.StartAsync（CancellationTokencancelToken）Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync（IHost主机，CancellationToken令牌）Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync（IHost主机，CancellationToken令牌）Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run（IHost主机）Program.cs中的Alpha.Web.App.Program.Main（string [] args）+CreateHostBuilder（args）.Build（）。Run（）;

显示原始异常详细信息InvalidOperationException：无法解决范围服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'来自根提供商。Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution（TypeserviceType，IServiceScope范围，IServiceScope rootScope）Microsoft.Extensions.DependencyInjection.ServiceProvider.Microsoft.Extensions.DependencyInjection.ServiceLookup.IServiceProviderEngineCallback.OnResolve（TypeserviceType，IServiceScope范围）Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService（TypeserviceType，ServiceProviderEngineScope（serviceProviderEngineScope）Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService（Type服务类型）Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（IServiceProvider提供者，输入serviceType）Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（IServiceProvider提供者）Alpha.DataAccess.ApplicationDbContext.CreateAdminAccount（IServiceProviderserviceProvider，IConfiguration配置）中ApplicationDbContext.cs+UserManager userManager = serviceProvider.GetRequiredService>（）;

显示原始异常详细信息System.InvalidOperationException：无法解决范围服务'Microsoft.AspNetCore.Identity.UserManager`1 [Alpha.Models.Identity.User]'来自根提供商。在Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution（TypeserviceType，IServiceScope范围，IServiceScope rootScope）位于Microsoft.Extensions.DependencyInjection.ServiceProvider.Microsoft.Extensions.DependencyInjection.ServiceLookup.IServiceProviderEngineCallback.OnResolve（TypeserviceType，IServiceScope范围）Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService（TypeserviceType，ServiceProviderEngineScope（serviceProviderEngineScope）在Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService（TypeserviceType）在Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（IServiceProvider提供者，输入serviceType）Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService [T]（IServiceProvider供应商）Alpha.DataAccess.ApplicationDbContext.CreateAdminAccount（IServiceProviderserviceProvider，IConfiguration配置）中E：\ Archives \ Projects \ Alpha \ Alpha.DataAccess \ ApplicationDbContext.cs：line92 .NET Core 3.0.0 X64 v4.0.0.0 | Microsoft.AspNetCore.Hosting版本3.0.0-rc2.19465.2 | Microsoft Windows 10.0.17763 |需要帮助吗？

Answer 1

从您随附的屏幕快照中，它表明您在Startup.Configure中包含以下行：

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

存储在IServiceProvider中的IApplicationBuilder.ApplicationServices实例是您的应用程序的root服务提供者。错误消息指出，它无法解析root服务提供者的scoped服务。

此问题经常出现，但是针对您的情况最简单的解决方案是将IApplicationBuilder.ApplicationServices注入您的IServiceProvider方法并将其传递到Configure：]

CreateAdminAccount
传递到public void Configure(IApplicationBuilder app, IServiceProvider serviceProvider)
{
    ApplicationDbContext.CreateAdminAccount(serviceProvider, Configuration)
        .Wait();
}
的IServiceProvider的实例是scoped

，这意味着您可以使用它来创建作用域服务。

这就是完成此工作所需的全部，但是在Configure中进行此类播种更为典型。这使种子关注点与配置管道分离，并且还允许使用Program / async。这是一个例子：

await
您也可以在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) =>
        // ...
}
中解析UserManager<User>和RoleManager<Role>，并将它们传递给Main，而不是使用服务定位器方法。