今天在阅读《CLR via C#》，书中说
“使用foreach语句时，会在finally块中调用IEnumerator对象的Dispose方法”（第20章 异常和状态管理，P434）
自己很奇怪的是，在编译foreach语句时也会生成try/finally语句块吗？会吧，不会吧！！
于是自己做了如下实验：
static void ILDiscoveryForeach()
{
var someList = Enumerable.Range(0, 10);
foreach (var item in someList)
{
}
}
使用ILDasm工具得到的IL语言如下：
.method private hidebysig static void ILDiscoveryForeach() cil managed
{
// Code size 46 (0x2e)
.maxstack 2
.locals init ([0] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> someList,
[1] class [mscorlib]System.Collections.Generic.IEnumerator`1<int32> CS$5$0000)
IL_0000: ldc.i4.0
IL_0001: ldc.i4.s 10
IL_0003: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32,
int32)
IL_0008: stloc.0
IL_0009: ldloc.0
IL_000a: callvirt instance class [mscorlib]System.Collections.Generic.IEnumerator`1<!0> class [mscorlib]System.Collections.Generic.IEnumerable`1<int32>::GetEnumerator() // 得到someList对象的枚举器
IL_000f: stloc.1
.try
{
IL_0010: br.s IL_0019 // 无条件跳转到19行
IL_0012: ldloc.1 // 将枚举器压入堆栈
IL_0013: callvirt instance !0 class [mscorlib]System.Collections.Generic.IEnumerator`1<int32>::get_Current() // 调用枚举器的get_Current()方法
IL_0018: pop //
IL_0019: ldloc.1 // 将枚举器压入堆栈
IL_001a: callvirt instance bool [mscorlib]System.Collections.IEnumerator::MoveNext() // 调用MoveNext()方法
IL_001f: brtrue.s IL_0012 // 如果返回值为true，则到12行
IL_0021: leave.s IL_002d // 如果遍历结束，则退出try语句块，到2d行，但之前会执行finally语句块的内容
} // end .try
finally
{
// 如果枚举器不为空，则调用枚举器的Dispose()方法！
IL_0023: ldloc.1
IL_0024: brfalse.s IL_002c
IL_0026: ldloc.1
IL_0027: callvirt instance void [mscorlib]System.IDisposable::Dispose()
IL_002c: endfinally
} // end handler
IL_002d: ret
} // end of method Program::ILDiscoveryForeach
从上面可以知道，Jeffery说的是对的，Dispose不是Enumerable对象，而是Enumerator对象!!
这样一切都很合理了。
但是对于一个数组对象的foreach遍历又是怎样的呢？
代码：
static void ILDiscoveryForeach()
{
int[] someList = { 1, 2, 3, 4, 5 };
foreach (var item in someList)
{
}
}
IL：
.method private hidebysig static void ILDiscoveryForeach() cil managed
{
// Code size 39 (0x27)
.maxstack 3
.locals init ([0] int32[] someList,
[1] int32[] CS$6$0000,
[2] int32 CS$7$0001)
IL_0000: ldc.i4.5
IL_0001: newarr [mscorlib]System.Int32
IL_0006: dup
IL_0007: ldtoken field valuetype '<PrivateImplementationDetails>{90173B59-8615-4757-89A1-22E0F30C78E3}'/'__StaticArrayInitTypeSize=20' '<PrivateImplementationDetails>{90173B59-8615-4757-89A1-22E0F30C78E3}'::'$$method0x6000001-1'
IL_000c: call void [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(class [mscorlib]System.Array,
valuetype [mscorlib]System.RuntimeFieldHandle)
IL_0011: stloc.0
IL_0012: ldloc.0 // 将数组对象压入栈
IL_0013: stloc.1 // 将数组指针赋值给位置1的变量
IL_0014: ldc.i4.0 // 常数0压入栈
IL_0015: stloc.2 // 赋值给位置2变量
IL_0016: br.s IL_0020
IL_0018: ldloc.1
IL_0019: ldloc.2
IL_001a: ldelem.i4
IL_001b: pop
IL_001c: ldloc.2
IL_001d: ldc.i4.1
IL_001e: add
IL_001f: stloc.2
IL_0020: ldloc.2
IL_0021: ldloc.1
IL_0022: ldlen
IL_0023: conv.i4
IL_0024: blt.s IL_0018
IL_0026: ret
} // end of method Program::ILDiscoveryForeach
阅读上面的代码，发现对于整数数组对象的foreach，编译器会编译成for(int i=0; i<length;i++)的方式编译。