单个查询中的EF多个聚合

本文介绍了单个查询中的EF多个聚合的处理方法，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

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.