实体框架 - Linq To Entities - 多对多查询问题

Question

我在查询Linq To Entities中的多对多关系时遇到问题.我基本上尝试使用Linq复制此查询:

Select * 
FROM Customer 
LEFT JOIN CustomerInterest ON Customer.CustomerID = CustomerInterest.CustomerID
LEFT JOIN Interest ON CustomerInterest.InterestID = Interest.InterestID
WHERE Interest.InterestName = 'Football'

我环顾网络并没有找到任何合适的例子来说明这一点.我最接近的是:

List<Customer> _Customers = (from _LCustomers in _CRM.Customer.Include("CustomerInterest.Interest")
                                  where _LCustomers.CustomerInterest.Any(x => x.Interest.InterestName == "Football")
                                  select _LCustomers).ToList();

这样做的问题是,如果客户有多个兴趣而其中一个是"足球",则返回所有这些兴趣.我也看过All()有逆问题,即只有他们有一个兴趣才会返回,而且只有足球,如果他们有两个,而其中一个不是足球,则不返回任何东西.

有人有任何想法吗？

Answer 1

试试这个,

var result = from c in ctx.Customer
             from i in c.Interest
             where i.InterestName == "Football"
             select c;

希望这可以帮助,

射线.

Answer 2

我不确定你想获得什么。具有客户兴趣和兴趣的客户列表？只需根据客户的兴趣开始查询即可。

context.CustomerInterest.
   Where(ci => ci.Interest.InterestName == "Football").
   Select(ci => new
   {
      Customer = ci.Customer,
      CustomerInterest = ci,
      Interest = ci.Interest
   });

但这是非常多余的。为什么不直接获取匹配的客户兴趣呢？

IEnumerable<CustomerInterest> customerInterests = context.CustomerInterest.
   Where(ci => ci.Interest.InterestName == "Football");

您仍然可以访问其他信息，而无需显式存储。

foreach (CustomerInterest customerInterest in customerInterests)
{
   DoSomething(customerInterest);
   DoSomething(customerInterest.Customer);
   DoSomething(customerInterest.Interest);
}