是否使用動態關鍵字導致泛型類型導致裝箱？

Question

以下代碼是否會導致傳入GenericMethod調用的整數被裝箱？

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

void Main() 
{ 
    GenericMethod(100); 
} 

Answer 1

根據C＃規範§4.7動態類型：

dynamic被認爲是等同於object除了在以下幾個方面：

• 上dynamic類型的表達式的運算可以是動態綁定（§7.2.2）。

• 類型推理（§7.5.2）將優先於dynamic而不是object，如果兩者都是候選者。

因此，鑄造dynamic原因拳以同樣的方式作爲鑄造object。

Answer 2

動態類型的變量被編譯到object類型的變量中，類型dynamic僅在編譯時存在，而不是在運行時存在。

因此，實際上您的示例會將其轉換爲引用類型的對象。拳擊這裏存在

Answer 3

讓我們來看看IL代碼，看是否拳擊是存在的：

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 

正如你可以從下面這行代碼，請參閱：

IL_003e: box !!T 

這盒詮釋