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var xs = (from x in dbContext.db_API_Operationallog where x.id<1 select 1 ).Count();
结果：
SELECT
[GroupBy1].[A1] AS [C1]
FROM ( SELECT
COUNT(1) AS [A1]
FROM [dbo].[db_API_Operationallog] AS [Extent1]
WHERE [Extent1].[id] < 1
) AS [GroupBy1]
context.db_API_Operationallog.FirstOrDefault(p => p.Id == postId).Hits;
或者：
context.db_API_Operationallog.Find(postId).Hits;
会把整个post表数据都查出然后再内存里面找了hits这个列
优化：
context.db_API_Operationallog.Where(p => p.Id == postId).Select(p => p.Hits).FirstOrDefault();
有时候一个不小心在查询的sql build 里面加了个tolist(), toArray()等，这种真正的执行了查询，这样在开发环境往往表的数据比较少，程序运行比较快，但是一到线上环境数据量比较大的情况下就会出现内存爆满的问题，这个问题相对来说比较隐蔽，所以开发的时候一定要小心。
public IEnumerable<db_API_Operationallog> GetAllPost()
{
return context.Post;
}
int id = 2000;
var log = GetAllPost().Where(s => s.id <id).ToList();
Sql Server Profiler 抓到的信息
SELECT [Extent1].[id] AS [id], [Extent1].[uid] AS [uid], [Extent1].[types] AS [types], [Extent1].[events] AS [events], [Extent1].[more] AS [more], [Extent1].[money] AS [money], [Extent1].[lastmoney] AS [lastmoney], [Extent1].[nowmoney] AS [nowmoney], [Extent1].[bak] AS [bak], [Extent1].[times] AS [times] FROM [dbo].[db_API_Operationallog] AS [Extent1]
exec sp_executesql N‘SELECT [Extent1].[id] AS [id], [Extent1].[uid] AS [uid], [Extent1].[types] AS [types], [Extent1].[events] AS [events], [Extent1].[more] AS [more], [Extent1].[money] AS [money], [Extent1].[lastmoney] AS [lastmoney], [Extent1].[nowmoney] AS [nowmoney], [Extent1].[bak] AS [bak], [Extent1].[times] AS [times] FROM [dbo].[db_API_Operationallog] AS [Extent1] WHERE [Extent1].[id] < @p__linq__0‘,N‘@p__linq__0 int‘,@p__linq__0=2000
这个坑是比较同样也是比较隐蔽的注意下
dbContext.db_API_Operationallog.Where(s => s.id < id).AsNoTracking().ToList();
平时写EF的时候一定要把脚步停下了 多使用 Sql Server Profiler 琢磨下自己的代码
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原文地址：http://www.cnblogs.com/echosong/p/5519772.html
