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LINQ菜鸟，我该如何编写这个常见的查询？

发布于 2024-12-10 10:52:24 字数 765 浏览 0 评论 0原文

我是一名长期开发人员，但对 LINQ 仍然很陌生。当处理一组对象时，我没问题，但是当我需要从多个来源获取数据时，事情会变得更加困难，并且我可以使用一些指导来获取我需要的东西。

我的数据库中有三个表，两个相关的表和一个保存 PK/FK 将它们连接在一起的表。例如：

Users

UserID
UserName

Surveys

SurveyID
SurveyName

UserSurveys

UserID
SurveyID

我正在使用EF，所以所有这些数据已被拉入对象中。

所以...我想要做的是返回与给定用户关联的所有调查的列表。所以类似（伪代码）：

// currentUserID = the UserID I need to get matching Surveys for
var surveys = from Survey where (s => s.SurveyID == UserSurvey.SurveyID && UserSurvey.UserID == currentUserID);

我假设我需要进行子查询并使用 Contains() 或类似的东西，但我一直被自己绊倒。帮助？

原文

I'm a long time dev, but still kind of new to LINQ. I'm OK when dealing with one set of object, but things get tougher when I need to pull from several sources, and I could use some guidance in getting what I need here.

I have three tables in my database, two related tables and one that holds the PK/FK to tie them together. So something like:

Users

UserID
UserName

Surveys

SurveyID
SurveyName

UserSurveys

UserID
SurveyID

I am using EF and so all of this data has been pulled into Objects.

So... what I want to do is return a List of all Surveys that are associated with a given User. So something like (pseudo-code):

// currentUserID = the UserID I need to get matching Surveys for
var surveys = from Survey where (s => s.SurveyID == UserSurvey.SurveyID && UserSurvey.UserID == currentUserID);

I assume I need to make a sub-query and use a Contains() or something like that, but I keep tripping over myself. Help?

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邮友 2024-12-17 10:52:24

应该是这样的：

from us in UserSurveys
where us.UserId == currentUserID
join s in Surveys on us.SurveyID equals s.SurveyID
select s

Should be something like this:

from us in UserSurveys
where us.UserId == currentUserID
join s in Surveys on us.SurveyID equals s.SurveyID
select s

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洛阳烟雨空心柳 2024-12-17 10:52:24

如果这是 EF，您应该能够进行 someUser.Surveys。

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老旧海报 2024-12-17 10:52:24

假设你的数据库和实体模型有你所有的 FK 引用，你应该能够做这样的事情......

// currentUserID = the UserID I need to get matching Surveys for 
var surveys = from s in Survey 
              where s.User.UserID == currentUserID
              select s;

Assuming your database and entity model has all of your FK references you should be able to do something like this....

// currentUserID = the UserID I need to get matching Surveys for 
var surveys = from s in Survey 
              where s.User.UserID == currentUserID
              select s;

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