问题出在UserManager上，这解决了问题.

The issue is with the UserManager, this solves the issue.

    ApplicationDbContext context = new ApplicationDbContext();

    var roleManager = new RoleManager<IdentityRole>(new RoleStore<IdentityRole>(context));
    var UserManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(context));
    UserManager.UserValidator = new UserValidator<ApplicationUser>(UserManager)
    {
        AllowOnlyAlphanumericUserNames = false,
        RequireUniqueEmail = true
    };

    string password = System.Web.Security.Membership.GeneratePassword(12, 4);
    var user = new ApplicationUser();
    user.Email = model.Email;
    user.UserName = model.Email;

    string userPWD = password;

    var result = UserManager.Create(user, userPWD);