foreach与for的性能比较

string[] strings = new string[] { "str1", "str2", "str3", "str4", "str5", "str6" };
            foreach (string s in strings)
            {
                textBox1.AppendText(s + "\r\n");
            }

IL：

            foreach (string s in strings)
000000e0  nop 
000000e1  mov         eax,dword ptr [ebp-44h] 
000000e4  mov         dword ptr [ebp-50h],eax 
000000e7  xor         edx,edx 
000000e9  mov         dword ptr [ebp-54h],edx 
000000ec  nop 
000000ed  jmp         00000136                       //jmp to J1
000000ef  mov         eax,dword ptr [ebp-54h] 
000000f2  mov         edx,dword ptr [ebp-50h] 
000000f5  cmp         eax,dword ptr [edx+4] 
000000f8  jb          000000FF 　　　　　　　　//低于"1个字节全是1"跳转 
000000fa  call        65C86690 　　　　　　　　//地址如此之大,应该是个外部call
000000ff  mov         eax,dword ptr [edx+eax*4+0Ch] 
00000103  mov         dword ptr [ebp-48h],eax 
            {
00000106  nop 
                textBox1.AppendText(s + "\r\n");
00000107  mov         eax,dword ptr [ebp-3Ch] 
0000010a  mov         eax,dword ptr [eax+00000140h] 
00000110  mov         dword ptr [ebp-60h],eax 
00000113  mov         edx,dword ptr ds:[027420A8h] 
00000119  mov         ecx,dword ptr [ebp-48h] 
0000011c  call        64EB50F0 　　　　　　　　　　//这个call可能是+导致的 不换行的话IL很短的
00000121  mov         dword ptr [ebp-64h],eax 
00000124  mov         edx,dword ptr [ebp-64h] 
00000127  mov         ecx,dword ptr [ebp-60h] 
0000012a  cmp         dword ptr [ecx],ecx 
0000012c  call        636C6414 　　　　　　　　　　
00000131  nop 
            }　　　　　　　　　　　　　　　　　　　　
00000132  nop 
00000133  inc         dword ptr [ebp-54h] 
            foreach (string s in strings)
00000136  mov         eax,dword ptr [ebp-54h]        //Here’s J1
00000139  mov         edx,dword ptr [ebp-50h] 
0000013c  cmp         eax,dword ptr [edx+4] 
0000013f  setl        al 
00000142  movzx       eax,al 
00000145  mov         dword ptr [ebp-58h],eax 
00000148  cmp         dword ptr [ebp-58h],0 
0000014c  jne         000000EF 

for的IL:

            for (int i = 0; i != 6; i++)
000000d6  xor         edx,edx 
000000d8  mov         dword ptr [ebp-48h],edx 
000000db  nop 
000000dc  jmp         0000011F 
            {
000000de  nop 
                textBox1.AppendText(strings[i] + "\r\n");
000000df  mov         eax,dword ptr [ebp-3Ch] 
000000e2  mov         eax,dword ptr [eax+00000140h] 
000000e8  mov         dword ptr [ebp-58h],eax 
000000eb  mov         eax,dword ptr [ebp-48h] 
000000ee  mov         edx,dword ptr [ebp-44h] 
000000f1  cmp         eax,dword ptr [edx+4] 
000000f4  jb          000000FB 
000000f6  call        65D56690 
000000fb  mov         ecx,dword ptr [edx+eax*4+0Ch] 
000000ff  mov         edx,dword ptr ds:[028620A8h] 
00000105  call        64F850F0 
0000010a  mov         dword ptr [ebp-5Ch],eax 
0000010d  mov         edx,dword ptr [ebp-5Ch] 
00000110  mov         ecx,dword ptr [ebp-58h] 
00000113  cmp         dword ptr [ecx],ecx 
00000115  call        63796414 
0000011a  nop 
            }
0000011b  nop 
            for (int i = 0; i != 6; i++)
0000011c  inc         dword ptr [ebp-48h] 
0000011f  cmp         dword ptr [ebp-48h],6 
00000123  setne       al 
00000126  movzx       eax,al 
00000129  mov         dword ptr [ebp-50h],eax 
0000012c  cmp         dword ptr [ebp-50h],0 
00000130  jne         000000DE 
        }

21个指令3个call

foreach的指令要多很多,应该是foreach慢一些,据<<更锋利的c#>>一书,foreach迭代要比for循环快速,因为这是专门优化的,但是执行效率不能说明问题,c#本机编译完成后,大概是PC上执行最快的local code,c++为什么看起来能节约几倍的执行时间?不是执行速度要有多快,重要是的,本地代码能少点不,搞tmd10倍,想快也快不起来.

那个作者说foreach快,我感觉for快.

foreach不是for的安全版再一个个弹出项吗,这能比for快吗,不过项很多的话,性能也许能超过for....