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Entity Framework 4 Linq 帮助 - 从过滤的多个表中提取数据

发布于 2024-10-16 09:46:09 字数 358 浏览 2 评论 0原文

不确定这是如何完成的，我设置了 .edmx，以便导航属性与表上的外键关系匹配。不确定我是否仍然需要执行联接，或者 EF 是否会让我通过导航属性自动访问相关表数据。

在此处输入图像描述

我需要做什么，根据 ContentView 获取所有 ContentSections 及其关联的 ContentItems 并按DiversionProgram.CrimeNumber。

我想取回 IEnumerable，对于每个 ContentSection，它应该可以通过导航属性 ContentItems 访问它的 ContentItems

谢谢

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分分钟 2024-10-23 09:46:09

比如：

using(Entities context = new Entities())
{
  IEnumerable<ContentSection> enumerator = context.ContentSections
  .Include("ContentItems")
  .Where<ContentSection>(cs => cs.ContentView.ContentViewID == someID && cs.ContentItems.Where<ContentItem>(ci => ci.DiversionProgram.CrimeNumber == someCrimeNumber))
  .AsEnumerable<ContentSection>
}

我已经解释过了

基于ContentView

作为 cs.ContentView.ContentViewID == someID

这将为您提供给定 ContentView 的所有 ContentSections。并解读

按 DiversionProgram.CrimeNumber 过滤

为 cs.ContentItems.Where(ci => ci.DiversionProgram.CrimeNumber == someCrimeNumber) ，

这将为您提供所有具有特定 CrimeNumber 的 ContentItem。

或者你的意思是基于/过滤的其他东西。也许是 OrderBy，或者所有那些 ContentSections，其中任何一个 ContentItems 都会有一个特定的 CrimeNumber？

Something like:

using(Entities context = new Entities())
{
  IEnumerable<ContentSection> enumerator = context.ContentSections
  .Include("ContentItems")
  .Where<ContentSection>(cs => cs.ContentView.ContentViewID == someID && cs.ContentItems.Where<ContentItem>(ci => ci.DiversionProgram.CrimeNumber == someCrimeNumber))
  .AsEnumerable<ContentSection>
}

I've interpreted

based on the ContentView

as cs.ContentView.ContentViewID == someID

This will give you all the ContentSections for a given ContentView. And interpreted

filtered by the DiversionProgram.CrimeNumber

as cs.ContentItems.Where<ContentItem>(ci => ci.DiversionProgram.CrimeNumber == someCrimeNumber)

which will give you all those ContentItems that have a specific CrimeNumber.

Or did you mean something else with based on / filtered by. Maybe OrderBy, or all those ContentSections where Any of it's ContentItems would have a certain CrimeNumber?

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毁虫ゝ 2024-10-23 09:46:09

您可以急切地加载以获取所有关联记录，但是当您想要开始过滤/排序时，不必担心包含。

只需使用匿名类型进行投影，EF 就会计算出它需要做什么。它有点毛茸茸的，但它会起作用。如果它变得太复杂，那就硬着头皮使用 SPROC。

现在，带着这个警告，类似这样的事情（从我的脑海中浮现出来）：

var query = ctx.ContentView
               .Select(x => new 
{
   ContentSections = x.ContentSections
                      .Where(y => y.ContentItems
                        .Any(z => z.DivisionProgram.CrimeNumber = 87))
}).ToList().Select(x => x.ContentSections);

You can eager load to get all associated records, but when you want to start filtering/ordering, don't bother with Include.

Just do a projection with anonymous types and EF will work out what it needs to do. It's a bit hairy, but it'll work. If it get's too complicated, bite the bullet and use a SPROC.

Now, with that caveat, something like this (off the top of my head):

var query = ctx.ContentView
               .Select(x => new 
{
   ContentSections = x.ContentSections
                      .Where(y => y.ContentItems
                        .Any(z => z.DivisionProgram.CrimeNumber = 87))
}).ToList().Select(x => x.ContentSections);

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断桥再见 2024-10-23 09:46:09

如果您使用 CTP5，您可以做一些非常独特的事情，如下所示：

var context = new YourEntitiesContext();

var query = context.ContentView.Include(cs => cs.ContentSections
                   .Select(ci => ci.ContentItems
                   .Select(dp => dp.DiversionProgram)
                   .Where(dp.CrimeNumber == crimeNumber)))
                   .Where(cv => cv.ContentViewID == contentViewID).FirtsOrDefault();

您可以了解有关 CTP5 的更多信息以及如何在数据库优先场景中使用它此处

If you use the CTP5 you can do something very unique it looks like this:

var context = new YourEntitiesContext();

var query = context.ContentView.Include(cs => cs.ContentSections
                   .Select(ci => ci.ContentItems
                   .Select(dp => dp.DiversionProgram)
                   .Where(dp.CrimeNumber == crimeNumber)))
                   .Where(cv => cv.ContentViewID == contentViewID).FirtsOrDefault();

You can learn more about the CTP5 and how it can be used in Database first scenario here

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慈悲佛祖 2024-10-23 09:46:09

 var query = from t1 in studentManagementEntities.StudentRegistrations
                        join t2 in studentManagementEntities.StudentMarks
                        on t1.StudentID equals t2.StudentID
                        select new
                        {
                            t1.selected column name,
                            t2.selected column name
                        };

 var query = from t1 in studentManagementEntities.StudentRegistrations
                        join t2 in studentManagementEntities.StudentMarks
                        on t1.StudentID equals t2.StudentID
                        select new
                        {
                            t1.selected column name,
                            t2.selected column name
                        };

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