我在Startup.cs中得到了这段代码：
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
services.AddIdentity<ApplicationUser, ApplicationRole>()
.AddEntityFrameworkStores<ApplicationDbContext>()
.AddDefaultTokenProviders();
在同一文件中，我还按照 MS 在新版 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，我得到了一个运行以下内容的 SeedDatabase 帮助程序方法：
var roleManager = serviceProvider.GetService<RoleManager<ApplicationRole>>();
这一切都工作正常，但是自从将VS 2017更新到最新版本并安装.NET Core 2.0以来，最后一行代码现在会引发以下异常：
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:gsandorxDocumentsVisual Studio 2017ProjectsCspLicensingPortalCspLicensingPortalStartup.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应用程序角色类。我已经检查过，我所有的引用都使用这个类，而不是默认的 IdentityRole。
有什么想法吗？
您必须自己创建 IServiceScope。
为此，您必须更换
var roleManager = serviceProvider.GetService<RoleManager<ApplicationRole>>();
跟
using (IServiceScope scope = app.ApplicationServices.CreateScope()) {
RoleManager<IdentityRole> roleManager = scope.ServiceProvider.GetRequiredService<RoleManager<IdentityRole>>();
// Seed database code goes here
}