使用LINQ查询三个实体. -包含路径表达式必须引用在类型上定义的导航属性 [英] Using LINQ to query three entitites. - Include path expression must refer to a navigation property defined on the type
问题描述
我正在尝试从3个实体中获取数据.考试,目的和目的细节.我希望能够通过考试名称来选择它.这是我正在使用的代码:
I am trying to get data from 3 entities. Exam, Objective and Objective detail. I want to be able to select this by exam name. Here is the code I am using:
var result = await db.Exams
.Include(e => e.Objectives)
.Include(e => e.Objectives.SelectMany(o => o.ObjectiveDetails))
.Where(e => e.Name == name)
.FirstOrDefaultAsync();
当我运行它时,这给我一个错误消息:
This is giving me an error message when I run it saying:
exceptionMessage =包含路径表达式必须引用一个 在类型上定义的导航属性.使用虚线路径 参考导航属性和用于收集的Select运算符 导航属性.参数名称:路径
exceptionMessage=The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties. Parameter name: path
有人可以告诉我我在做什么错.这是我的课程:
Can someone advise me what I am doing wrong. Here's my classes:
public class Exam
{
public Exam()
{
this.Objectives = new HashSet<Objective>();
}
public int ExamId { get; set; }
public int SubjectId { get; set; }
public virtual ICollection<Objective> Objectives { get; set; }
}
public class Objective : AuditableTable
{
public Objective()
{
this.ObjectiveDetails = new HashSet<ObjectiveDetail>();
}
public int ObjectiveId { get; set; }
public int ExamId { get; set; }
public int Number { get; set; }
public virtual Exam Exam { get; set; }
public virtual ICollection<ObjectiveDetail> ObjectiveDetails { get; set; }
}
public partial class ObjectiveDetail
{
public int ObjectiveDetailId { get; set; }
public int ObjectiveId { get; set; }
public int Number { get; set; }
public string Text { get; set; }
public virtual Objective Objective { get; set; }
}
推荐答案
使用Select
代替SelectMany:
.Include(e => e.Objectives.Select(o => o.ObjectiveDetails))
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