如何建模层次结构 [英] How to Model Hierarchies

问题描述

我想对任务组建模，以便一个任务可以有多个子任务，一个子任务可以分配给许多任务。



我的实体看起来像这样：



公共课程任务

{

    public long Id {get;组; }


    public string Name {get;组; }
}



公共类任务组

{

    public long Id {get;组; }


    public long ParentTaskId {get;组; }


    [ForeignKey（" ParentTaskId"）]
$
    public virtual Task ParentTask {get;组; }


    public long ChildTaskId {get;组; }


    [ForeignKey（" ChildTaskId"）]
$
    public virtual Task ChildTask {get;组; }


    public byte Level {get;组; }
}



我明确定义交叉点实体，因为我必须保留额外信息（等级）。



我是否必须在enitity Task中声明如下内容，以便我能够进行查询

，例如"db.Tasks.Where（t） => t.ParentTasks.Count == 0）;"在没有父母的情况下完成任务？

  &NBSP; public virtual ICollection< TaskGroup> ParentTasks {get;组; }¥b $ b  &NBSP; public virtual ICollection< TaskGroup> ChildTasks {得到;组; }


如何在EF中建立这样的层次结构。



我尝试了很多，但没有工作得非常满意。

非常感谢。

I want to model groups of tasks so that one task can have many subtasks and one subtask can be assigned to many tasks.

My Entities look like this:

public class Task
{
    public long Id { get; set; }

    public string Name { get; set; }
}

public class TaskGroup
{
    public long Id { get; set; }

    public long ParentTaskId { get; set; }

    [ForeignKey("ParentTaskId")]
    public virtual Task ParentTask { get; set; }

    public long ChildTaskId { get; set; }

    [ForeignKey("ChildTaskId")]
    public virtual Task ChildTask { get; set; }

    public byte Level { get; set; }
}

I explicitly define the intersection entity as I have to persist extra information (Level).

Do I have to declare something like the following in enitity Task, so that I'm able to make queries
such as "db.Tasks.Where(t => t.ParentTasks.Count == 0);" to get the tasks with no parent?
    public virtual ICollection<TaskGroup> ParentTasks { get; set; }
    public virtual ICollection<TaskGroup> ChildTasks { get; set; }

How can you model such a hierarchy in EF.

I tried a lot, but nothing worked satisfactorily.
Thanks a lot.

推荐答案

罗马T öngi，

>>我是否必须在enitity Task中声明类似以下的内容，以便我能够进行查询

这样的as"db.Tasks.Where（t => t.ParentTasks.Count == 0）;"得到没有父母的任务？

>>Do I have to declare something like the following in enitity Task, so that I'm able to make queries
such as "db.Tasks.Where(t => t.ParentTasks.Count == 0);" to get the tasks with no parent?

根据你的描述，似乎我们可以在任务类中添加一个字段，如下所示：

Based on your description, it seems that we could add a field in task class, like this:

public class Task
 {
     public long Id { get; set; }

     public string TaskType { get; set; }

     public string Name { get; set; }
 }

然后你可以像这样过滤ParentTask：

Then you could filter ParentTask like this:

db.Tasks.Where(t => t.TaskType == "Parent");

祝你好运，

Cole Wu

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