第一种：

 private ApplicationUserManager _userManager;
public ApplicationUserManager UserManager
        {
            get
            {
                return _userManager ?? HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>();

            }
            private set
            {
                _userManager = value;
            }
        }

第二种：

var store = new UserStore<ApplicationUser>(context);
var manager =  new ApplicationUserManager(store);
var user = new ApplicationUser() { Email = "informatyka4444@wp.pl", UserName = "informatyka4444@wp.pl" };
manager.Create(user, "TestPass44!");