描述:项目中使用了linq,发现写的顺序不一样最后的结果也不一样,效率也不一样。

Linq的执行效率对比
List<int> source = new List<int>(); var rand = new Random(); int i = 5000;
while (i > 0) { i--; source.Add(rand.Next(1, 500)); } Stopwatch watch = new
Stopwatch(); 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