实体框架多个罪名单一查询 [英] Entity Framework multiple counts with a single query

问题描述

很抱歉，如果这已被问过，但我怎么能改善到数据库的单一调用下面？

  VAR statsModel =新
{
     总= _db.Messages.Count（）
     批准= _db.Messages.Count（X =＆GT; x.Approved）
     拒绝= _db.Messages.Count（X =＆GT;！x.Approved）
};
 

解决方案

首先，你可以计算拒绝由道达尔和接受这样的：

 拒绝=总 - 批准
 

和进一步改进可以在拍摄同时计算他们的;

 从_db.Messages米
让总= _db.Messages.Count（）
让接受= _db.Messages.Count（X =＆GT; x.Approved == true）而
选择新的{总，接受}）
 

更新：
现在一个简单的黑客：只取第一行

 （从_db.Messages米
让总= _db.Messages.Count（）
让接受= _db.Messages.Count（X =＆GT; x.Approved == true）而
选择新的{总，接受}）采取（1）。
 

但我在寻找一个更清洁的有一个

Sorry if this has been asked, but how can I improve the following with a single call to the database?

var statsModel = new
{
     Total = _db.Messages.Count(),
     Approved = _db.Messages.Count(x => x.Approved),
     Rejected = _db.Messages.Count(x => !x.Approved),
};

解决方案

First of all you can compute the Rejected by Total and Accepted like this:

Rejected = Total - Approved

And for further improvement you can compute both of them in on shot;

from m in _db.Messages
let Total =  _db.Messages.Count()
let Accept = _db.Messages.Count(x => x.Approved == true)
select new {Total , Accept})

UPDATE: a simple hack for now : just take the first row

(from m in _db.Messages
let Total =  _db.Messages.Count()
let Accept = _db.Messages.Count(x => x.Approved == true)
select new {Total , Accept}).Take(1);

But I'm looking for a cleaner one

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