IUserPasswordStore Casting问题

Question

我有这堂课：

internal class UserRepository : Repository<User>, IUserPasswordStore<User>, IUserLoginStore<User>
{
    public UserRepository(DbContext context)
        : base(context)
    {
    }

    public Task<string> GetPasswordHashAsync(User user)
    {
        if (user == null)
            throw new ArgumentNullException("user");

        return Task.FromResult<string>(user.PasswordHash);
    }

    public Task<bool> HasPasswordAsync(User user)
    {
        return Task.FromResult<bool>(user.PasswordHash != null);
    }

    public Task SetPasswordHashAsync(User user, string passwordHash)
    {
        if (user == null)
            throw new ArgumentNullException("user");

        user.PasswordHash = passwordHash;

        return Task.FromResult<int>(0);
    }

    public Task AddLoginAsync(User user, UserLoginInfo login)
    {
        throw new NotImplementedException();
    }

    public Task<User> FindAsync(UserLoginInfo login)
    {
        throw new NotImplementedException();
    }

    public Task<IList<UserLoginInfo>> GetLoginsAsync(User user)
    {
        throw new NotImplementedException();
    }

    public Task RemoveLoginAsync(User user, UserLoginInfo login)
    {
        throw new NotImplementedException();
    }

    #region NotUsed

    public void Dispose()
    {
        throw new NotImplementedException();
    }

    public Task CreateAsync(User user)
    {
        throw new NotImplementedException();
    }

    public Task DeleteAsync(User user)
    {
        throw new NotImplementedException();
    }

    public Task<User> FindByIdAsync(string userId)
    {
        throw new NotImplementedException();
    }

    public Task<User> FindByNameAsync(string userName)
    {
        throw new NotImplementedException();
    }

    public Task UpdateAsync(User user)
    {
        throw new NotImplementedException();
    }

    #endregion

}

在我的服务中我有这个：

public class UserService : Service<User>
{
    private readonly string companyId;

    public IPasswordHasher PasswordHasher { get; set; }
    public IIdentityValidator<string> PasswordValidator { get; set; }
    public IIdentityValidator<User> UserValidator { get; set; }
    public ClaimsIdentityFactory ClaimsIdentityFactory { get; set; }

    public virtual bool SupportsUserSecurityStamp { get { return this.Repository is IUserSecurityStampStore<User>; } }

    public UserService(IUnitOfWork uow, string companyId)
        : base (uow)
    {
        this.PasswordHasher = new PasswordHasher();
        this.UserValidator = new UserValidator(this);
        this.PasswordValidator = new MinimumLengthValidator(6);
        this.ClaimsIdentityFactory = new ClaimsIdentityFactory();

        this.companyId = companyId;
    }

    private IUserPasswordStore<User> GetPasswordStore()
    {
        var userPasswordStore = this.Repository as IUserPasswordStore<User>;
        if (userPasswordStore == null)
            throw new NotSupportedException(Resources.StoreNotIUserPasswordStore);

        return userPasswordStore;
    }
}

GetPasswordStore 是问题所在。 userPasswordStore 始终为null，即使存储库正在实现它。

为清楚起见，这是服务类：

public class Service<T> where T : class
{
    private readonly IRepository<T> repository;

    protected IRepository<T> Repository
    {
        get { return this.repository; }
    }

    internal Service(IUnitOfWork unitOfWork)
    {
        this.repository = unitOfWork.GetRepository<T>();
    }
}

任何人都可以将 UserRepository 作为 IUserPasswordStore 返回null吗？ 我会盲目地盯着它看：）