For 和 Foreach 的比较

C#代码：
public int LoopTest()
{
int s=0;

int[] array={2,3,4,5,6,7,8,9};

for(int k=0;k<=7;k++)
{
s+=array[k];
}

foreach(int a in array)
{
s+=a;
}

return s;

}

IL代码：
.method public hidebysig instance int32 LoopTest() cil managed
{
// 代码大小 78 (0x4e)
.maxstack 3
.locals init ([0] int32 s,
[1] int32[] 'array',
[2] int32 k,
[3] int32 a,
[4] int32 CS$00000003$00000000,
[5] int32[] CS$00000007$00000001,
[6] int32 CS$00000008$00000002)
IL_0000: ldc.i4.0
IL_0001: stloc.0
IL_0002: ldc.i4.8
IL_0003: newarr [mscorlib]System.Int32
IL_0008: dup
IL_0009: ldtoken field valuetype '

 1<privateimplementationdetails>'/'$$struct0x6000002-1' '<privateimplementationdetails>'::'$$method0x6000002-1'   
 2IL_000e: call void [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(class [mscorlib]System.Array,   
 3valuetype [mscorlib]System.RuntimeFieldHandle)   
 4IL_0013: stloc.1   
 5IL_0014: ldc.i4.0   
 6IL_0015: stloc.2   
 7IL_0016: br.s IL_0022 //for 开始的地方   
 8IL_0018: ldloc.0   
 9IL_0019: ldloc.1   
10IL_001a: ldloc.2   
11IL_001b: ldelem.i4   
12IL_001c: add   
13IL_001d: stloc.0   
14IL_001e: ldloc.2   
15IL_001f: ldc.i4.1   
16IL_0020: add   
17IL_0021: stloc.2   
18IL_0022: ldloc.2   
19IL_0023: ldc.i4.7   
20IL_0024: ble.s IL_0018 //for 结束的地方   
21IL_0026: ldloc.1 //foreach 从这里开始   
22IL_0027: stloc.s CS$00000007$00000001   
23IL_0029: ldc.i4.0   
24IL_002a: stloc.s CS$00000008$00000002   
25IL_002c: br.s IL_003e   
26IL_002e: ldloc.s CS$00000007$00000001   
27IL_0030: ldloc.s CS$00000008$00000002   
28IL_0032: ldelem.i4   
29IL_0033: stloc.3   
30IL_0034: ldloc.0   
31IL_0035: ldloc.3   
32IL_0036: add   
33IL_0037: stloc.0   
34IL_0038: ldloc.s CS$00000008$00000002   
35IL_003a: ldc.i4.1   
36IL_003b: add   
37IL_003c: stloc.s CS$00000008$00000002   
38IL_003e: ldloc.s CS$00000008$00000002   
39IL_0040: ldloc.s CS$00000007$00000001   
40IL_0042: ldlen   
41IL_0043: conv.i4   
42IL_0044: blt.s IL_002e //foreach结束的地方   
43IL_0046: ldloc.0   
44IL_0047: stloc.s CS$00000003$00000000 //此乃自动生成的一个变量，保存返回值，void时没有   
45IL_0049: br.s IL_004b   
46IL_004b: ldloc.s CS$00000003$00000000   
47IL_004d: ret   
48} // end of method Class1::LoopTest</privateimplementationdetails></privateimplementationdetails>