父/子表未在 LINQ 中引用，还是我错了？

发布于 2024-09-08 05:05:37 字数 783 浏览 0 评论 0原文

我有一个类别表“类别”[ID，标题]和一个父/子表“CategoryParent”[ID，CategoryID，ParentCategoryID]，其中多对多树由使用 ParentCategoryID 指示的类别的父级表示连接表中的字段。

我认为这将是一个简单的结构，用于检索根类别（在连接表中具有 NULL 作为 ParentCategoryID 值的类别条目）和子类别（按父 id）。

但是，我没有尝试编写 LINQ2SQL 语句来通过连接表中的父 ID 获取类别对象的列表，已生成任何可编译的内容。

我会发布一些代码，但从任何角度来看，它们都不是（a）完整的或（b）合理的。

应该如何解决这个问题呢？

我的连接表如下所示：

CategoryParent
---
ParentCategoryID [int] (PK)
CategoryID [int] FK
CategoryParentID [int] FK

我的数据（类别）表如下所示：

Category
---
CategoryID [int] PK
Title [nvarchar]

有两种关系：

Category.CategoryID 1->* CategoryParent.CategoryID
Category.CategoryID 1->* CategoryParent.ParentCategoryID

我想提供 NULL 或 CategoryID 并获取以其作为父级的所有类别表行。

原文

I have a categories table "Category" [ID, Title] and a Parent/Child table "CategoryParent" [ID,CategoryID,ParentCategoryID] where a many-to-many tree is represented by the parent of a category being indicated using the ParentCategoryID field in the join table.

I thought this would be a simple structure to use to retrieve root categories (category entries which have NULL as a ParentCategoryID value in the join table) and child categories (by parent id.)

However, none of my attempts to write a LINQ2SQL statement to get a list of Category objects by their parent ID in the join table have produced anything compilable.

I would post some code, but none of it is either (a)complete or (b)sensible - in any terms at all.

How should one go about this?

My join table looks like this:

CategoryParent
---
ParentCategoryID [int] (PK)
CategoryID [int] FK
CategoryParentID [int] FK

My data (category) table looks like this:

Category
---
CategoryID [int] PK
Title [nvarchar]

There are two relationships:

Category.CategoryID 1->* CategoryParent.CategoryID
Category.CategoryID 1->* CategoryParent.ParentCategoryID

I would like to provide either NULL or a CategoryID and get back all the Category table rows which have it as a parent.

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缺⑴份安定 2024-09-15 05:05:37

好吧，看来我应该做的是使用 LINQ 进行相当基本的联接，而不是依赖于上下文类中的联接对象。像这样的东西：

var props = from i in context.Prices
    join e in context.PricingEntities on i.EntityID equals e.EntityID
    join l in context.PricingEntityProperties on e.EntityID equals l.EntityID
    join p in context.PricingProperties on l.PropertyID equals p.PropertyID
    where i.InstanceID == instanceId
    select p;

Ok, well, it looks like what I should have been doing is a fairly basic join using LINQ, rather than relying on the join objects in the context class. Something like:

var props = from i in context.Prices
    join e in context.PricingEntities on i.EntityID equals e.EntityID
    join l in context.PricingEntityProperties on e.EntityID equals l.EntityID
    join p in context.PricingProperties on l.PropertyID equals p.PropertyID
    where i.InstanceID == instanceId
    select p;

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