HttpContext.GetOwinContext().GetUserManager() 返回 null

我使用 ASP.NET Identity 2 创建角色，但结果是HttpContext.GetOwinContext().GetUserManager<AppRoleManager>()为空。

然后我就无法创建这个角色。

我怎么解决这个问题？

public class MVCController : Controller
{
    public MVCController()
    {

    }
    public AppRoleManager RoleManager // returns null ?!
    {
        get
        {
            return HttpContext.GetOwinContext().GetUserManager<AppRoleManager>();
        }
    }
    public User CurrentUser
    {
        get
        {
            string currentUserId = User.Identity.GetUserId();
            User currentUser = DataContextFactory.GetDataContext().Users.FirstOrDefault(x => x.Id.ToString() == currentUserId);
            return currentUser;
        }
    }
    public IAuthenticationManager AuthManager
    {
        get
        {

            return HttpContext.GetOwinContext().Authentication;
        }
    }
    public AppUserManager UserManager
    {
        get
        {
            return HttpContext.GetOwinContext().GetUserManager<AppUserManager>();
        }
    }
} 

我的控制器：

public class RoleAdminController : MVCController
{
    [HttpPost]
    public async Task<ActionResult> CreateRole([Required]string name)
    {
        if (ModelState.IsValid)
        {
            if (RoleManager != null) // RoleManager is null, why?!
            {
                IdentityResult result = await RoleManager.CreateAsync(new Role { Name = name });
                if (result.Succeeded)
                {
                    return RedirectToAction("Index");
                }
                else
                {
                    AddErrorsFromResult(result);
                }
            }
        }
        return View(name);
    }
}

应用角色管理器：

public class AppRoleManager : RoleManager<Role, int>, IDisposable
{
    public AppRoleManager(RoleStore<Role, int, UserRole> store)
        : base(store)
    {
    }
    public static AppRoleManager Create(IdentityFactoryOptions<AppRoleManager> options, IOwinContext context)
    {
        return new AppRoleManager(new RoleStore<Role, int, UserRole>(DataContextFactory.GetDataContext()));
    }
}

您很可能错过了为 OwinContext 提供创建 ApplicationUserManager 的方法。
为此，您需要将这些放入您的public void Configuration(IAppBuilder app)

app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
app.CreatePerOwinContext<AppRoleManager>(AppRoleManager.Create);

这将注册创建的代表UserManager and RoleManager with OwinContext只有在那之后你才能在控制器中回调它们。