詳解C#例項化物件的三種方式及效能對比

阿新 • • 發佈：2020-12-12

前言

做專案過程中有個需求要例項化兩萬個物件並新增到List

中，這個過程大概需要1min才能載入完（傳參較多），於是開啟了程式碼優化之旅，再此記錄。

首先想到的是可能例項化比較耗時，於是開始對每種例項化方式進行測試，過程如下

例項化方式

1、用 New 關鍵字例項化一個類

2、用 Activator 例項化一個類

3、用 Assembly 例項化一個類

程式碼實現

測試環境：

vs2019 .NET Framework 4.7

Intel Core i7-10510U CPU

首先定義一個類Person

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

我們先在無參的建構函式中例項化，每種方式進行十次，每次例項化十萬次，程式碼如下

static void Main(string[] args)
  {
   Console.WriteLine("例項化物件的耗時比較（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();
  }

執行結果如下：

詳解C#例項化物件的三種方式及效能對比

然後來看下有參建構函式中例項化的程式碼和結果

static void Main(string[] args)
  {
   Console.WriteLine("例項化物件的耗時比較（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);
     person = obj as Person;
    }
    watch.Stop();
    Console.Write(watch.ElapsedMilliseconds.ToString().PadLeft(5));
   }
   Console.Write("\n");
   Console.ReadKey();
  }

執行結果如下：

詳解C#例項化物件的三種方式及效能對比