是否使用动态关键字导致泛型类型导致装箱？

Question

以下代码是否会导致传入GenericMethod调用的整数被装箱？

void GenericMethod<T>(T value) 
{ 
    int test = (dynamic)value; 
} 

void Main() 
{ 
    GenericMethod(100); 
} 

Answer 1

根据C＃规范§4.7动态类型：

dynamic被认为是等同于object除了在以下几个方面：

• 上dynamic类型的表达式的运算可以是动态绑定（§7.2.2）。

• 类型推理（§7.5.2）将优先于dynamic而不是object，如果两者都是候选者。

因此，铸造dynamic原因拳以同样的方式作为铸造object。

Answer 2

动态类型的变量被编译到object类型的变量中，类型dynamic仅在编译时存在，而不是在运行时存在。

因此，实际上您的示例会将其转换为引用类型的对象。拳击这里存在

Answer 3

让我们来看看IL代码，看是否拳击是存在的：

IL_0000: nop 
IL_0001: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>> class Test.Program/'<>o__0`1'<!!T>::'<>p__0' 
IL_0006: brfalse.s IL_000a 
IL_0008: br.s IL_002e 
IL_000a: ldc.i4.0 
IL_000b: ldtoken [mscorlib]System.Int32 
IL_0010: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle) 
IL_0015: ldtoken Test.Program 
IL_001a: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle) 
IL_001f: call class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, class [mscorlib]System.Type, class [mscorlib]System.Type) 
IL_0024: call class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder) 
IL_0029: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>> class Test.Program/'<>o__0`1'<!!T>::'<>p__0' 
IL_002e: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>> class Test.Program/'<>o__0`1'<!!T>::'<>p__0' 
IL_0033: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>>::Target 
IL_0038: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>> class Test.Program/'<>o__0`1'<!!T>::'<>p__0' 
IL_003d: ldarg.0 
IL_003e: box !!T 
IL_0043: callvirt instance int32 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, int32>::Invoke(!0, !1) 
IL_0048: stloc.0 
IL_0049: ret 

正如你可以从下面这行代码，请参阅：

IL_003e: box !!T 

这盒诠释