(31)Know your loops

招数31：

认识你的循环

for is the fastest way of iterating over a collection, foreach is a little slower, and LINQ queries are slowest.

for是遍历集合最快的方法，foreach略慢一些，LINQ查询最慢。

测试代码：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Data;using System.Diagnostics;namespace ConsoleApplicationExample{    class Program    {        static void Main(string[] args)        {            Console.WriteLine("code test:");            Stopwatch watch = new Stopwatch();            // for loop            watch.Start();            for (int i = 0; i < 100000; i++) { ; }            watch.Stop();            Console.WriteLine("for loop:");            Console.WriteLine(watch.Elapsed.TotalMilliseconds);            watch = new Stopwatch();            // while loop            watch.Start();            int loop = 0;            while (loop < 100000) { loop++; }            watch.Stop();            Console.WriteLine("while loop:");            Console.WriteLine(watch.Elapsed.TotalMilliseconds);            watch = new Stopwatch();            // foreach loop            watch.Start();            int[] array = new int[100000];            foreach (int i in array) { ; }            watch.Stop();            Console.WriteLine("foreach loop:");            Console.WriteLine(watch.Elapsed.TotalMilliseconds);            watch = new Stopwatch();            // foreach loop            watch.Start();            Array.ForEach(array, (i) => { ; });            watch.Stop();            Console.WriteLine("lamda loop:");            Console.WriteLine(watch.Elapsed.TotalMilliseconds);            Console.ReadLine();        }    }}

 

测试结果：

code test:for loop:0.2467while loop:0.2666foreach loop:0.4867lamda loop:0.8728