如果condition为true，则实体框架linq内部连接返回对象

Question

public UserMaster Login(UserMaster userMaster, string otp)
    {

        return (from um in _context.UserMasters.Where(u => u.UserName == userMaster.UserName && u.Password == userMaster.Password && u.IsDisplay == true && u.IsActive == true)
                join pin in _context.UserPins.Where(p => p.Pin == otp) on um.UserId equals pin.UserId
                select new { um }).SingleOrDefault();
   }

如果条件满足，我试图返回User的对象，即如果用户具有正确的pass和username以及来自不同表的正确otp。我只需要/要求返回用户主对象。

给出以下错误

Answer 1

public UserMaster Login(UserMaster userMaster, string otp)
{
       return (from um in _context.UserMasters.Where(u => u.UserName == userMaster.UserName && u.Password == userMaster.Password && u.IsDisplay == true && u.IsActive == true)
              join pin in _context.UserPins.Where(p => p.Pin == otp) on um.UserId equals pin.UserId
              select um).FirstOrDefault();
}