ASP.NET Core 2 - 身份 - 自定义角色的 DI 错误

Question

我的 Startup.cs 中有这段代码：

 services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddIdentity<ApplicationUser, ApplicationRole>()
            .AddEntityFrameworkStores<ApplicationDbContext>()
            .AddDefaultTokenProviders();

在同一个文件中，我还按照 MS 在新版本 ASP Core 2 中的建议将 service.UseIdentity() 替换为 app.UseAuthentication();。

我的数据库上下文：

 public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string>
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
        // Customize the ASP.NET Identity model and override the defaults if needed.
        // For example, you can rename the ASP.NET Identity table names and more.
        // Add your customizations after calling base.OnModelCreating(builder);
    }


    //public DbSet<ApplicationUser> ApplicationUser { get; set; }

    //public DbSet<ApplicationRole> ApplicationRole { get; set; }
}

还有我的自定义角色类：

 public class ApplicationRole : IdentityRole
{
    public ApplicationRole() : base() { }

    public ApplicationRole(string roleName) : base(roleName) { }

    public bool IsDefault { get; set; }
}

运行应用程序时，我得到了一个运行的 SeedDatabase 辅助方法：

var roleManager = serviceProvider.GetService<RoleManager<ApplicationRole>>();

一切正常，但自从将 VS 2017 更新到最新版本并安装 .NET Core 2.0 后，这最后一行代码现在引发以下异常：

System.AggregateException occurred
HResult=0x80131500
Message=One or more errors occurred. (Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.RoleManager`1[CspLicensingPortal.Models.ApplicationRole]' from root provider.)
Source=<Cannot evaluate the exception source>
StackTrace:
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at System.Threading.Tasks.Task.Wait()
at CspLicensingPortal.Startup.Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory) in D:\gsandorx\Documents\Visual Studio 2017\Projects\CspLicensingPortal\CspLicensingPortal\Startup.cs:line 275

Inner Exception 1:
InvalidOperationException: Cannot resolve scoped service 'Microsoft.AspNetCore.Identity.RoleManager`1[MyApplication.Models.ApplicationRole]' from root provider.

我不确定为什么 DI 服务管理器不再能够找到我的 ApplicationRole 类。我已经检查过，我所有的引用都在使用这个类，而不是默认的 IdentityRole。

有什么想法吗？

Answer 1

您必须自己创建 IServiceScope。

要做到这一点，你必须更换

var roleManager = serviceProvider.GetService<RoleManager<ApplicationRole>>();

与

using (IServiceScope scope = app.ApplicationServices.CreateScope()) {
    RoleManager<IdentityRole> roleManager = scope.ServiceProvider.GetRequiredService<RoleManager<IdentityRole>>();

    // Seed database code goes here
}