如何使用linq联接3个表 [英] How to join 3 tables with linq

问题描述

我正在尝试使用Linq在查询中联接3个表以从所有3个表中获取数据.下面是表方案的图像:

I am trying to join 3 tables in a query with Linq to get data from all 3 tables. Below is an image of the table schemes:

查询应选择:SewagePlantName，CompanyName和Duty

The query should select: SewagePlantName, CompanyName and Duty

此外，我需要将SewagePlantId限制为以以下形式给出的ID列表:

In addition I need to restricts the SewagePlantId to a list of Ids that are given as:

            var sewagePlantIds = UnitOfWork.GetAll<UserGroup>()
            .Where(group => group.Id == webAppPrincipal.GroupId)
            .SelectMany(group => group.SewagePlantId).Select(sewageplant => sewageplant.Id).ToList();

在连接3个表的顺序以及将SewagePlantId限制在给定列表的位置/方式方面，我遇到了困难.

I have difficulties with the order of joining the 3 tables and where/how to restrict the SewagePlantId to the given list.

推荐答案

可以加入类似的东西吗

from d in Duty
join c in Company on d.CompanyId equals c.id
join s in SewagePlant on c.SewagePlantId equals s.id
select new
  {
      duty = s.Duty.Duty, 
      CatId = s.Company.CompanyName,
      SewagePlantName=s.SewagePlant.SewagePlantName
      // other assignments
  };

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