实体框架linq查询Include（）多个子实体

Question

这可能是一个非常重要的问题，但是当编写跨越三个级别（或更多）的查询时，包含多个子实体的好方法是什么？

即我有4个表：Company，Employee，Employee_Car和Employee_Country

公司与员工有1：m的关系。

Employee与Employee_Car和Employee_Country的关系为1：m。

如果我想编写一个返回所有4个表中数据的查询，我目前正在编写：

Company company = context.Companies

                         .Include("Employee.Employee_Car")

                         .Include("Employee.Employee_Country")

                         .FirstOrDefault(c => c.Id == companyID);

必须有一个更优雅的方式！这是漫长的缠绕，并产生可怕的SQL

我在VS 2010中使用EF4

Answer 1

使用扩展方法。将NameOfContext替换为对象上下文的名称。public static class Extensions{&nbsp; &nbsp;public static IQueryable<Company> CompleteCompanies(this NameOfContext context){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;return context.Companies&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.Include("Employee.Employee_Car")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.Include("Employee.Employee_Country") ;&nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp;public static Company CompanyById(this NameOfContext context, int companyID){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;return context.Companies&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.Include("Employee.Employee_Car")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.Include("Employee.Employee_Country")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;.FirstOrDefault(c => c.Id == companyID) ;&nbsp; &nbsp; &nbsp; }}然后你的代码变成了&nbsp; &nbsp; &nbsp;Company company =&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; context.CompleteCompanies().FirstOrDefault(c => c.Id == companyID);&nbsp; &nbsp; &nbsp;//or if you want even more&nbsp; &nbsp; &nbsp;Company company =&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; context.CompanyById(companyID);