单个查询中的EF多个聚合 [英] EF multiple aggregate in single query

问题描述

我想根据不同的条件来计算集合的数量：

I want to get count of a set based on different condition:

 var invoices = new AccountingEntities().Transactions
 var c1 = invoices.Count(i=>i.Type = 0);
 var c2 = invoices.Count(i=>i.Type = 1);
 var c3 = invoices.Count(i=>i.Type = 2);

如何在一次DB往返中调用所有三个查询以提高性能？

How its possible to call all three queries in one DB round trip to increase performance?

推荐答案

当然，只需将您的三个计数用POCO或匿名类型包装起来即可：

Sure, just wrap up your three counts in a POCO or anonymous type:

using (var invoices = new AccountingEntities())
{
    var c = (from i in invoices.Transactions
             select new 
             {
                 c1 = invoices.Count(i=>i.Type = 0),
                 c2 = invoices.Count(i=>i.Type = 1),
                 c3 = invoices.Count(i=>i.Type = 2)
             }).Single();           
}

另外，如我所示，处理上下文。

Also, dispose your context, as I show.

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