C# 闭包对像

主要内容：

1、描述出现的现像

2、分析其出现的原因

3、提示

一、看如下一段代码及结果

 class Program
     {
         static void Main(string[] args)
         {
             List<Action> lists = new List<Action>();
             for (int i = ; i < ; i++)
             {

                 Action t = () =>
                     {

                         Console.WriteLine(i.ToString());
                     };
                 lists.Add(t);
             }
             foreach (var t in lists)
             {
                 t();
             }

             Console.Read();
         }
     }

 class Program
     {
         static void Main(string[] args)
         {
             List<Action> lists = new List<Action>();
             for (int i = ; i < ; i++)
             {
                 int temp = i;
                 Action t = () =>
                     {
                         Console.WriteLine(temp.ToString());

                     };
                 lists.Add(t);
             }
             foreach (var t in lists)
             {
                 t();
             }

             Console.Read();
         }
     }

为什么加了一个临时变量就结果不一样了呢？

二、现像分析

我们查看第一段代码的il和第二段的il

 .method private hidebysig static void  Main(string[] args) cil managed
 {
   .entrypoint
   // 代码大小       149 (0x95)
   .maxstack
   .locals init ([] class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action> lists,
            [] class [mscorlib]System.Action t,
            [] class [mscorlib]System.Action 'CS$<>9__CachedAnonymousMethodDelegate1',
            [] class iltest.Program/'<>c__DisplayClass2' 'CS$<>8__locals3',
            [] bool CS$$,
            [] valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action> CS$$)
   IL_0000:  nop
   IL_0001:  newobj     instance void class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::.ctor()
   IL_0006:  stloc.
   IL_0007:  ldnull
   IL_0008:  stloc.
   IL_0009:  newobj     instance void iltest.Program/'<>c__DisplayClass2'::.ctor()
   IL_000e:  stloc.
   IL_000f:  ldloc.
   IL_0010:  ldc.i4.
   IL_0011:  stfld      int32 iltest.Program/'<>c__DisplayClass2'::i
   IL_0016:  br.s       IL_0044
   IL_0018:  nop
   IL_0019:  ldloc.
   IL_001a:  brtrue.s   IL_002b
   IL_001c:  ldloc.
   IL_001d:  ldftn      instance void iltest.Program/'<>c__DisplayClass2'::'<Main>b__0'()
   IL_0023:  newobj     instance void [mscorlib]System.Action::.ctor(object,
                                                                     native int)
   IL_0028:  stloc.
   IL_0029:  br.s       IL_002b
   IL_002b:  ldloc.
   IL_002c:  stloc.
   IL_002d:  ldloc.
   IL_002e:  ldloc.
   IL_002f:  callvirt   instance void class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::Add(!)
   IL_0034:  nop
   IL_0035:  nop
   IL_0036:  ldloc.
   IL_0037:  dup
   IL_0038:  ldfld      int32 iltest.Program/'<>c__DisplayClass2'::i
   IL_003d:  ldc.i4.
   IL_003e:  add
   IL_003f:  stfld      int32 iltest.Program/'<>c__DisplayClass2'::i
   IL_0044:  ldloc.
   IL_0045:  ldfld      int32 iltest.Program/'<>c__DisplayClass2'::i
   IL_004a:  ldc.i4.
   IL_004b:  clt
   IL_004d:  stloc.s    CS$$
   IL_004f:  ldloc.s    CS$$
   IL_0051:  brtrue.s   IL_0018
   IL_0053:  nop
   IL_0054:  ldloc.
   IL_0055:  callvirt   instance valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<!> class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::GetEnumerator()
   IL_005a:  stloc.s    CS$$
   .try
   {
     IL_005c:  br.s       IL_006f
     IL_005e:  ldloca.s   CS$$
     IL_0060:  call       instance ! valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>::get_Current()
     IL_0065:  stloc.
     IL_0066:  nop
     IL_0067:  ldloc.
     IL_0068:  callvirt   instance void [mscorlib]System.Action::Invoke()
     IL_006d:  nop
     IL_006e:  nop
     IL_006f:  ldloca.s   CS$$
     IL_0071:  call       instance bool valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>::MoveNext()
     IL_0076:  stloc.s    CS$$
     IL_0078:  ldloc.s    CS$$
     IL_007a:  brtrue.s   IL_005e
     IL_007c:  leave.s    IL_008d
   }  // end .try
   finally
   {
     IL_007e:  ldloca.s   CS$$
     IL_0080:  constrained. valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>
     IL_0086:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
     IL_008b:  nop
     IL_008c:  endfinally
   }  // end handler
   IL_008d:  nop
   IL_008e:  call       int32 [mscorlib]System.Console::Read()
   IL_0093:  pop
   IL_0094:  ret
 } // end of method Program::Main

 .method private hidebysig static void  Main(string[] args) cil managed
 {
   .entrypoint
   // 代码大小       127 (0x7f)
   .maxstack
   .locals init ([] class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action> lists,
            [] int32 i,
            [] class [mscorlib]System.Action t,
            [] class iltest.Program/'<>c__DisplayClass1' 'CS$<>8__locals2',
            [] bool CS$$,
            [] valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action> CS$$)
   IL_0000:  nop
   IL_0001:  newobj     instance void class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::.ctor()
   IL_0006:  stloc.
   IL_0007:  ldc.i4.
   IL_0008:  stloc.
   IL_0009:  br.s       IL_0033
   IL_000b:  newobj     instance void iltest.Program/'<>c__DisplayClass1'::.ctor()
   IL_0010:  stloc.
   IL_0011:  nop
   IL_0012:  ldloc.
   IL_0013:  ldloc.
   IL_0014:  stfld      int32 iltest.Program/'<>c__DisplayClass1'::temp
   IL_0019:  ldloc.
   IL_001a:  ldftn      instance void iltest.Program/'<>c__DisplayClass1'::'<Main>b__0'()
   IL_0020:  newobj     instance void [mscorlib]System.Action::.ctor(object,
                                                                     native int)
   IL_0025:  stloc.
   IL_0026:  ldloc.
   IL_0027:  ldloc.
   IL_0028:  callvirt   instance void class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::Add(!)
   IL_002d:  nop
   IL_002e:  nop
   IL_002f:  ldloc.
   IL_0030:  ldc.i4.
   IL_0031:  add
   IL_0032:  stloc.
   IL_0033:  ldloc.
   IL_0034:  ldc.i4.
   IL_0035:  clt
   IL_0037:  stloc.s    CS$$
   IL_0039:  ldloc.s    CS$$
   IL_003b:  brtrue.s   IL_000b
   IL_003d:  nop
   IL_003e:  ldloc.
   IL_003f:  callvirt   instance valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<!> class [mscorlib]System.Collections.Generic.List`<class [mscorlib]System.Action>::GetEnumerator()
   IL_0044:  stloc.s    CS$$
   .try
   {
     IL_0046:  br.s       IL_0059
     IL_0048:  ldloca.s   CS$$
     IL_004a:  call       instance ! valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>::get_Current()
     IL_004f:  stloc.
     IL_0050:  nop
     IL_0051:  ldloc.
     IL_0052:  callvirt   instance void [mscorlib]System.Action::Invoke()
     IL_0057:  nop
     IL_0058:  nop
     IL_0059:  ldloca.s   CS$$
     IL_005b:  call       instance bool valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>::MoveNext()
     IL_0060:  stloc.s    CS$$
     IL_0062:  ldloc.s    CS$$
     IL_0064:  brtrue.s   IL_0048
     IL_0066:  leave.s    IL_0077
   }  // end .try
   finally
   {
     IL_0068:  ldloca.s   CS$$
     IL_006a:  constrained. valuetype [mscorlib]System.Collections.Generic.List`/Enumerator<class [mscorlib]System.Action>
     IL_0070:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
     IL_0075:  nop
     IL_0076:  endfinally
   }  // end handler
   IL_0077:  nop
   IL_0078:  call       int32 [mscorlib]System.Console::Read()
   IL_007d:  pop
   IL_007e:  ret
 } // end of method Program::Main

就是相当于这种代码

  class Program
     {
         static void Main(string[] args)
         {
             List<Action> lists = new List<Action>();
             TempClass tc = new TempClass();

             for ( tc.i = ; tc.i < ; tc.i++)
             {
                 Action t = tc.FuncWrite;
                 lists.Add(t);
             }
             foreach (var t in lists)
             {
                 t();
             }

             Console.Read();
         }
     }
     class TempClass
     {
         public int i;
         public void FuncWrite()
         {
             Console.WriteLine(i.ToString());
         }

     }

说一个查看il 进入命令行，ildasm

理论分析以后补上。