IEnumerator的Current属性，是否在foreach时会自动类型转换?

[tlzjff]

MSDN上抄了段代码学习，发现IEnumerator的Current属性是一个object类型，但是在foreach的时候却能自动根据in前面的类型去自动匹配，调试时候断点进入Current
属性，因为Current返回的是一个object而我foreach里遍历类型却是一个CLASS，Class=object应该会报错呀，难道foreach里面会帮你类型转换么？为了证明这一点，
我用ildasmc查看了IL的代码
虽然里面基本都看不懂，不过有一行
L_0079: callvirt instance bool [mscorlib]System.Collections.IEnumerator::MoveNext()
猜测是在foreach时候调用的～
因为本人看不懂IL的代码，所以不知道IL里面哪里一行是类型转换，以证明foreach时会自动转换类型，
以下具体贴出.CS代码和IL代码，望高手指点我foreach迷津

C#代码

 public class MyIEnumberableAndIEnumberatorTest
    {
        public void DemoStart()
        {
            Person[] pe = new Person[10];
            for (int i = 0; i < pe.Length; i++)
            {
                pe[i] = new Person(i.ToString(), Convert.ToString(i * i));
            }
            People po = new People(pe);
            string str="";

            foreach (Person a in po)
            {
                str += a.firstName + a.lastName;
                Person aa = a;
            }
        }


        public class Person
        {
            public Person(string fName, string lName)
            {
                this.firstName = fName;
                this.lastName = lName;
            }

            public string firstName;
            public string lastName;
        }


        public class People : IEnumerable
        {
            private Person[] _people;
            public People(Person[] pArray)
            {
                _people = new Person[pArray.Length];

                for (int i = 0; i < pArray.Length; i++)
                {
                    _people[i] = pArray[i];
                }
            }

            public IEnumerator GetEnumerator()
            {
                return new PeopleEnum(_people);
            }
        }

        public class PeopleEnum : IEnumerator
        {
            public Person[] _people;

            // Enumerators are positioned before the first element
            // until the first MoveNext() call.
            int position = -1;

            public PeopleEnum(Person[] list)
            {
                _people = list;
            }

            public bool MoveNext()
            {
                position++;
                return (position < _people.Length);
            }

            public void Reset()
            {
                position = -1;
            }

            public object Current
            {
                get
                {
                    try
                    {
                        return _people[position];
                    }
                    catch (IndexOutOfRangeException)
                    {
                        throw new InvalidOperationException();
                    }
                }
            }
        }
    }

.method public hidebysig instance void  DemoStart() cil managed
{
  // コード サイズ       165 (0xa5)
  .maxstack  5
  .locals init ([0] class ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person[] pe,
           [1] int32 i,
           [2] class ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/People po,
           [3] string str,
           [4] class ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person a,
           [5] class ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person aa,
           [6] bool CS$4$0000,
           [7] class [mscorlib]System.Collections.IEnumerator CS$5$0001,
           [8] class [mscorlib]System.IDisposable CS$0$0002)
  IL_0000:  nop
  IL_0001:  ldc.i4.s   10
  IL_0003:  newarr     ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person
  IL_0008:  stloc.0
  IL_0009:  ldc.i4.0
  IL_000a:  stloc.1
  IL_000b:  br.s       IL_002a
  IL_000d:  nop
  IL_000e:  ldloc.0
  IL_000f:  ldloc.1
  IL_0010:  ldloca.s   i
  IL_0012:  call       instance string [mscorlib]System.Int32::ToString()
  IL_0017:  ldloc.1
  IL_0018:  ldloc.1
  IL_0019:  mul
  IL_001a:  call       string [mscorlib]System.Convert::ToString(int32)
  IL_001f:  newobj     instance void ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person::.ctor(string,
                                                                                                         string)
  IL_0024:  stelem.ref
  IL_0025:  nop
  IL_0026:  ldloc.1
  IL_0027:  ldc.i4.1
  IL_0028:  add
  IL_0029:  stloc.1
  IL_002a:  ldloc.1
  IL_002b:  ldloc.0
  IL_002c:  ldlen
  IL_002d:  conv.i4
  IL_002e:  clt
  IL_0030:  stloc.s    CS$4$0000
  IL_0032:  ldloc.s    CS$4$0000
  IL_0034:  brtrue.s   IL_000d
  IL_0036:  ldloc.0
  IL_0037:  newobj     instance void ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/People::.ctor(class ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person[])
  IL_003c:  stloc.2
  IL_003d:  ldstr      ""
  IL_0042:  stloc.3
  IL_0043:  nop
  IL_0044:  ldloc.2
  IL_0045:  callvirt   instance class [mscorlib]System.Collections.IEnumerator ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/People::GetEnumerator()
  IL_004a:  stloc.s    CS$5$0001
  .try
  {
    IL_004c:  br.s       IL_0077
    IL_004e:  ldloc.s    CS$5$0001
    IL_0050:  callvirt   instance object [mscorlib]System.Collections.IEnumerator::get_Current()
    IL_0055:  castclass  ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person
    IL_005a:  stloc.s    a
    IL_005c:  nop
    IL_005d:  ldloc.3
    IL_005e:  ldloc.s    a
    IL_0060:  ldfld      string ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person::firstName
    IL_0065:  ldloc.s    a
    IL_0067:  ldfld      string ConsoleApplication1.MyIEnumberableAndIEnumberatorTest/Person::lastName
    IL_006c:  call       string [mscorlib]System.String::Concat(string,
                                                                string,
                                                                string)
    IL_0071:  stloc.3
    IL_0072:  ldloc.s    a
    IL_0074:  stloc.s    aa
    IL_0076:  nop
    IL_0077:  ldloc.s    CS$5$0001
    IL_0079:  callvirt   instance bool [mscorlib]System.Collections.IEnumerator::MoveNext()
    IL_007e:  stloc.s    CS$4$0000
    IL_0080:  ldloc.s    CS$4$0000
    IL_0082:  brtrue.s   IL_004e
    IL_0084:  leave.s    IL_00a3
  }  // end .try
  finally
  {
    IL_0086:  ldloc.s    CS$5$0001
    IL_0088:  isinst     [mscorlib]System.IDisposable
    IL_008d:  stloc.s    CS$0$0002
    IL_008f:  ldloc.s    CS$0$0002
    IL_0091:  ldnull
    IL_0092:  ceq
    IL_0094:  stloc.s    CS$4$0000
    IL_0096:  ldloc.s    CS$4$0000
    IL_0098:  brtrue.s   IL_00a2
    IL_009a:  ldloc.s    CS$0$0002
    IL_009c:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_00a1:  nop
    IL_00a2:  endfinally
  }  // end handler
  IL_00a3:  nop
  IL_00a4:  ret
} // end of method MyIEnumberableAndIEnumberatorTest::DemoStart

[周公]

Person[] pe = new Person[10];
.....
foreach (Person a in po)
{
str += a.firstName + a.lastName;
Person aa = a;
}

你对一个Person数组用foreach，它使用了一些内部机制的。

[wuyq11]

IEnumerable的GetEnumerator返回一个实现了IEnumerator接口的对象
实现IEnumerable接口的类，可以支持foreach循环遍历对象的集合元素
参考

[指间的风]

观赏

[tlzjff]

自己顶

[zlb789]

学习

[outou]

[Quote=引用 2 楼 zhoufoxcn 的回复:]
C# codePerson[] pe = new Person[10];
.....
foreach (Person a in po)
{
str += a.firstName + a.lastName;
Person aa = a;
}


你对一个Person数组用foreach，它使用了一些内部机制的。
[/Quote]
支持

[yan286093636]

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