Linq包含where子句

本文介绍了Linq包含where子句的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

嘿，所以我遇到的情况是我从数据库中取回客户端，并通过包含所有案例研究包括

Hey so I've got the situation where I'm pulling a client back from the database and including all the case studies with it by way of an include

return (from c in db.Clients.Include("CaseStudies")
        where c.Id == clientId
        select c).First();

但我现在要做的是和包含的casestudies的where子句，以便它只返回案例研究删除=假

but what I want to do now is and a where clause on the included casestudies so that it only returns the case studies where deleted = false

有点像这样

return (from c in db.Clients.Include("CaseStudies")
        where c.Id == clientId
        && c.CaseStudy.Deleted == false
        select c).First();

但这不起作用:(任何想法

But this doesn't work :( any ideas

推荐答案

EF v1.0中不支持开箱即用的条件包含。但Alex James有一些hacky解决方法，因为这里解释得很好：

Conditional includes are not supported out-of-the-box in EF v1.0. But Alex James has a bit hacky workaround for that explained well here: http://blogs.msdn.com/alexj/archive/2009/10/13/tip-37-how-to-do-a-conditional-include.aspx

 var dbquery =
   from c in db.Clients
   where c.Id == clientID
   select new {
      client = c,
      caseStudies = from cs in c.CaseStudy
                where cs.Deleted==false
                select cs
   };

return dbquery
   .AsEnumerable()
   .Select(c => c.client);

此外，我没有成功地使这种解决方法适用于多对多关系。

Also, I haven't succeeded to make this workaround work with many-to-many relationships.

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