C# 4.0 新特性探秘 (三)：dynamic 關鍵字效能分析與原始 IL 代碼完整呈現

效能預期

動態語言固有綁定開銷，演算法設計對效能影響更大。功能與性能需平衡。

原始 IL 代碼 (完整)

.class private auto ansi beforefieldinit Program extends [mscorlib]System.Object
{
  .method private hidebysig static void Main() cil managed
  {
    .entrypoint
    .maxstack 9
    .locals init ([0] object d, [1] class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo[] CS$0$0000)
    L_0000: ldstr "str"
    L_0005: stloc.0
    L_0006: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>> Xianfen.Net.TestDynamic.Program/<Main>o__SiteContainer0::<>p__Site1
    L_000b: brtrue.s L_003f
    L_000d: ldc.i4.0
    L_000e: ldstr "ToString"
    L_0013: ldtoken Xianfen.Net.TestDynamic.Program
    L_0018: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
    L_001d: ldnull
    L_001e: ldc.i4.1
    L_001f: newarr [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo
    L_0024: stloc.1
    L_0025: ldloc.1
    L_0026: ldc.i4.0
    L_0027: ldc.i4.0
    L_0028: ldnull
    L_0029: newobj instance void [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::.ctor(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
    L_002e: stelem.ref
    L_002f: ldloc.1
    L_0030: newobj instance void [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpInvokeMemberBinder::.ctor(...)
    L_0035: call class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
    L_003a: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>> Xianfen.Net.TestDynamic.Program/<Main>o__SiteContainer0::<>p__Site1
    L_003f: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>> Xianfen.Net.TestDynamic.Program/<Main>o__SiteContainer0::<>p__Site1
    L_0044: ldfld !0 [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>>::Target
    L_0049: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>> Xianfen.Net.TestDynamic.Program/<Main>o__SiteContainer0::<>p__Site1
    L_004e: ldloc.0
    L_004f: callvirt instance void [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>::Invoke(!0, !1)
    L_0054: ret
  }
}
.class abstract auto ansi sealed nested private beforefieldinit <Main>o__SiteContainer0 extends [mscorlib]System.Object
{
  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor()
  .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`2<class [System.Core]System.Runtime.CompilerServices.CallSite, object>> <>p__Site1
}

IL 關鍵點

• ldstr "str" / stloc.0：字串賦值給 object 區域變數。
• ldsfld / brtrue.s：檢查靜態快取是否已建立。
• CSharpInvokeMemberBinder 綁定器建構：封裝呼叫資訊（方法名、型別、參數資訊）。
• CallSite.Create 建立快取項目並存入靜態欄位。
• CallSite.Target.Invoke 執行動態調度。

完整 IL 展示 DLR 基礎設施開銷：綁定器建構、快取查找、委派調用。