.NET Framework delegate performance?

自從 C# 3.0 (VS2008) 引入 anonymous method, 我很愛用這個, 但是記得曾經看過 delegate performance 不如 virtual function 好,
所以寫個小程式試驗.
在知道結果之後, 有找到官方說法:

The Truth about Delegates

其中有提到 : "Delegates are efficient. Invoking a delegate is as fast as invoking a virtual method."

那就看看程式執行結果吧:

Code:

   1: using System;
   2: using System.Collections.Generic;
   3: using System.Text;
   4:  
   5: namespace DelegatePerformance
   6: {
   7:     class Program
   8:     {        
   9:         static void Main(string[] args)
  10:         {
  11:             for (int i = 0; i < 5; i++)
  12:             {
  13:                 int testtimes = 100000000;
  14:                 test1 t1 = new test1(delegate() { return 0; });
  15:                 test2 t2 = new test2();
  16:                 test1 t3 = new test1(new test1.SimpleDelegate(f1));
  17:                 test1 t4 = new test1(new test1.SimpleDelegate(new Program().f2));
  18:                 DateTime begin1 = DateTime.Now;
  19:                 t1.dofunction(testtimes);
  20:                 DateTime end1 = DateTime.Now;
  21:                 DateTime begin2 = DateTime.Now;
  22:                 t2.dofunction(testtimes);
  23:                 DateTime end2 = DateTime.Now;
  24:                 DateTime begin3 = DateTime.Now;
  25:                 t3.dofunction(testtimes);
  26:                 DateTime end3 = DateTime.Now;
  27:                 DateTime begin4 = DateTime.Now;
  28:                 t4.dofunction(testtimes);
  29:                 DateTime end4 = DateTime.Now;
  30:                 Console.WriteLine("delegate:" + (end1 - begin1).ToString() + " , without delegate:" + (end2 - begin2).ToString() + " , delegate2:" + (end3 - begin3).ToString() + " , delegate3:" + (end4 - begin4).ToString());
  31:             }
  32:         }
  33:         static int f1()
  34:         {
  35:             return 0;
  36:         }
  37:         int f2()
  38:         {
  39:             return 0;
  40:         }
  41:     }
  42:  
  43:     class test1
  44:     {
  45:         public delegate int SimpleDelegate();
  46:  
  47:         private SimpleDelegate msd;
  48:         public test1(SimpleDelegate sd)
  49:         {
  50:             msd = sd;
  51:         }
  52:  
  53:         public void dofunction(int times)
  54:         {
  55:             for (int i = 0; i < times; i++)
  56:                 msd();
  57:         }
  58:     }
  59:  
  60:     class test2
  61:     {
  62:         private int ssd()
  63:         {
  64:             return 0;
  65:         }
  66:  
  67:         public test2()
  68:         {
  69:         }
  70:  
  71:         public void dofunction(int times)
  72:         {
  73:             for (int i = 0; i < times; i++)
  74:                 ssd();
  75:         }
  76:     }
  77: }
執行結果:
delegate:00:00:00.9740000 , without delegate:00:00:00.7070000 , delegate2:00:00:01.0150000 , delegate3:00:00:00.8260000
delegate:00:00:00.9470000 , without delegate:00:00:00.6970000 , delegate2:00:00:01.0150000 , delegate3:00:00:00.8230000
delegate:00:00:00.9500000 , without delegate:00:00:00.6930000 , delegate2:00:00:01.0110000 , delegate3:00:00:00.8260000
delegate:00:00:00.9500000 , without delegate:00:00:00.7030000 , delegate2:00:00:01.0110000 , delegate3:00:00:00.8240000
delegate:00:00:00.9530000 , without delegate:00:00:00.6950000 , delegate2:00:00:01.0190000 , delegate3:00:00:00.8350000

 
看樣子差不了多少...雖然有慢一點點, 不過以一億次 times 的scale 應該還好.