Question

我在一个模型中有多个表的类，如下所示：

public partial class Nurse
{
    public long Id { get; set; }
    public Nullable<System.Guid> Guid { get; set; }
    public long UserId { get; set; }
    public string Name {get;set;}
    public User user {get;set;}
}

我想像这样使用join用所有详细信息填充Nurse类的所有数据。

public List<Nurse> GetCareNurses(int id)
{
     var result = (from r in _context.Nurses
                          join u in _context.Users on r.UserId equals u.Id
                          where r.sector_id == id
                          select new Nurse { UserId = r.UserId, Name=u.FirstName+" " +u.LastName }).ToList();

    return result.ToList();              
}

它应该仅填充我在两个表中都需要的2个字段的数据，但会以The entity or complex type 'WatsonModel.Nurse' cannot be constructed in a LINQ to Entities query.的形式抛出错误。

Answer 1

您不能投影到映射的实体（护士），但是可以投影到匿名类型或数据传输对象（DTO）来传递数据。

如果您创建NurseDTO：

public class NurseDTO
{
    public string UserId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

然后致电GetCareNurses：

//Change 1: Change your List to List of type NurseDTO
 public List<NurseDTO> GetCareNurses(int id)
{
     var result = (from r in _context.Nurses
                          join u in _context.Users on r.UserId equals u.Id
                          where r.sector_id == id
                          //Change 2: Select new NurseDTO
                          select new NurseDTO { UserId = r.UserId, Name=u.FirstName+" " +u.LastName }).ToList();

    return result.ToList();              
}

您应该返回NurseDTO列表

Linq查询复杂类型模型

1 个答案: