教你50招提升ASP.NET性能（二十）：认识你的循环

(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 = ; i < ; i++) { ; }

            watch.Stop();

            Console.WriteLine("for loop:");

            Console.WriteLine(watch.Elapsed.TotalMilliseconds);

            watch = new Stopwatch();

            // while loop

            watch.Start();

            int loop = ;

            while (loop < ) { loop++; }

            watch.Stop();

            Console.WriteLine("while loop:");

            Console.WriteLine(watch.Elapsed.TotalMilliseconds);

            watch = new Stopwatch();

            // foreach loop

            watch.Start();

            int[] array = new int[];

            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:

0.2467

while loop:

0.2666

foreach loop:

0.4867

lamda loop:

0.8728

巴特西

教你50招提升ASP.NET性能（二十）：认识你的循环

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