Question

使用下面的方法我怎么能写出这个没有错误

return _session.Query<Data.Model.User>().Select(_userMapper.CreateUser)
          .AsQueryable();

但写下这个

return _session.Query<Data.Model.User>().Where(x => x.Username == username)
         .First(_userMapper.CreateUser);

产生错误。

public User CreateUser(Data.Model.User modelUser)
{
    return new User{UserId = modelUser.UserId, Username = modelUser.Username,
                    Email = modelUser.Email, Firstname = modelUser.Firstname,
                    Lastname = modelUser.lastname};
}

是否返回集合或单个项目，我希望它由create user方法转换。

Answer 1

您需要在Select之前致电First()：

return _session.Query<Data.Model.User>()
               .Where(x => x.Username == username)
               .Select(_userMapper.CreateUser)
               .First();

或者：

return _session.Query<Data.Model.User>()
               .Select(_userMapper.CreateUser)
               .First(x => x.Username == username);

Answer 2

return _userMapper.CreateUser(_session.Query<Data.Model.User>().First(x => x.Username == username));

Linq类型转换委托为.First方法

2 个答案: