watch.Restart(); var temp2 = from s in source orderby s where s > 100 select s; int count2 = temp2.Count(); watch.Stop(); Console.WriteLine( " orderby s where s > 100: " + watch.ElapsedTicks); watch.Restart(); var temp1 = from s in source where s > 100 orderby s select s; int count = temp1.Count(); watch.Stop(); Console.WriteLine( " where s > 100 orderby s: " + watch.ElapsedTicks);

效果如图：

效率相差还是蛮大的，差不多10倍，所以linq的执行要按照一定的顺序，不能随心所欲。

Linq优化

linq和sql的语法差不多，所以可以按照sql的执行顺序对linq进行优化，建议顺序

1.FROM
2.join
3.WHERE

4.GROUP BY

5.ORDER BY

6.SELECT

linq详解

https://www.cnblogs.com/zhao123/p/5621841.html