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詳解C#實(shí)例化對(duì)象的三種方式及性能對(duì)比

更新時(shí)間：2020年12月11日 08:44:22 作者：背過(guò)手

這篇文章主要介紹了C#實(shí)例化對(duì)象的三種方式及性能對(duì)比，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

前言

做項(xiàng)目過(guò)程中有個(gè)需求要實(shí)例化兩萬(wàn)個(gè)對(duì)象并添加到List

中，這個(gè)過(guò)程大概需要1min才能加載完（傳參較多），于是開(kāi)啟了代碼優(yōu)化之旅，再此記錄。

首先想到的是可能實(shí)例化比較耗時(shí)，于是開(kāi)始對(duì)每種實(shí)例化方式進(jìn)行測(cè)試，過(guò)程如下

實(shí)例化方式

1、用 New 關(guān)鍵字實(shí)例化一個(gè)類

2、用 Activator 實(shí)例化一個(gè)類

3、用 Assembly 實(shí)例化一個(gè)類

代碼實(shí)現(xiàn)

測(cè)試環(huán)境：

vs2019 .NET Framework 4.7

Intel Core i7-10510U CPU

首先定義一個(gè)類Person

public class Person 
{ 
 public Person()
 {
 }
 public Person(string name)
 {
  Name = name;
 }
 public string Name { get; set; }
}

我們先在無(wú)參的構(gòu)造函數(shù)中實(shí)例化，每種方式進(jìn)行十次，每次實(shí)例化十萬(wàn)次，代碼如下

static void Main(string[] args)
  {
   Console.WriteLine("實(shí)例化對(duì)象的耗時(shí)比較（單位：毫秒）");
   Console.Write("     ");
   for (int i = 1; i <= 10; i++)
    Console.Write("{0:G}", i.ToString().PadLeft(5));
   Console.Write("\n");
   Console.Write("InstanceByNew".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Person person = null;
    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
     person = new Person();
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.Write("InstanceByActivator".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Type type = Type.GetType("ConsoleApp1.Person");
    Person person = null;

    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
    {
     object obj = Activator.CreateInstance(type);
     person = obj as Person;
    }
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.Write("InstanceByAssembly".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Assembly assembly = Assembly.Load("InstancePerformance");
    Person person = null;

    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
    {
     object obj = assembly.CreateInstance("ConsoleApp1.Person");
     person = obj as Person;
    }
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.ReadKey();
  }

執(zhí)行結(jié)果如下：

然后來(lái)看下有參構(gòu)造函數(shù)中實(shí)例化的代碼和結(jié)果

static void Main(string[] args)
  {
   Console.WriteLine("實(shí)例化對(duì)象的耗時(shí)比較（單位：毫秒）");
   Console.Write("     ");
   for (int i = 1; i <= 10; i++)
    Console.Write("{0:G}", i.ToString().PadLeft(5));
   Console.Write("\n");
   Console.Write("InstanceByNew".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Person person = null;
    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
     person = new Person("Test"+j);
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.Write("InstanceByActivator".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Type type = Type.GetType("ConsoleApp1.Person");
    Person person = null;

    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
    {
     object obj = Activator.CreateInstance(type,new object[]{"Test"+j});
     person = obj as Person;
    }
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.Write("InstanceByAssembly".PadRight(20));
   for (int i = 1; i <= 10; i++)
   {
    Assembly assembly = Assembly.Load("InstancePerformance");
    Person person = null;

    Stopwatch watch = new Stopwatch();
    watch.Start();
    for (int j = 0; j < 100000; j++)
    {
     object obj = assembly.CreateInstance("ConsoleApp1.Person", true, System.Reflection.BindingFlags.Default, null, new []{"Test"+j}, null, null);
     person = obj as Person;
    }
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.ReadKey();
  }

執(zhí)行結(jié)果如下：

結(jié)論

從上面的執(zhí)行結(jié)果可以看出這三種方式的性能排序?yàn)?/p>

New > Activator > Assembly

但使用哪種方法還要視情況而定

后續(xù)

以上可以看出New性能最高，而我就是使用的New，問(wèn)題還沒(méi)解決，把問(wèn)題指向判斷List是否存在某元素上，于是開(kāi)始測(cè)試List中的Contains, Exists, Any，Where。詳情請(qǐng)點(diǎn)擊.

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