Question

我们想动态创建一个类，构造函数如下：

public JsRF1013Wrapper(ScriptEngine scriptEngine, string jsFileFullPath)
{
    this.ScriptEngine = scriptEngine;
    var jsFileContent = File.ReadAllText(jsFileFullPath);
    this.ScriptEngine.Execute(jsFileContent);
}

我们得到了IL：

.method public hidebysig specialname rtspecialname 
instance void  .ctor(class [ClearScript]Microsoft.ClearScript.ScriptEngine scriptEngine,
                     string jsFileFullPath) cil managed
{
    // Code size       37 (0x25)
    .maxstack  2
    .locals init ([0] string jsFileContent)
    IL_0000:  ldarg.0
    IL_0001:  call       instance void [mscorlib]System.Object::.ctor()
    IL_0006:  nop
    IL_0007:  nop
    IL_0008:  ldarg.0
    IL_0009:  ldarg.1
    IL_000a:  stfld      class [ClearScript]Microsoft.ClearScript.ScriptEngine TotalTaxation.TaxformCalculationUnitTests.JsRF1013Wrapper::ScriptEngine
    IL_000f:  ldarg.2
    IL_0010:  call       string [mscorlib]System.IO.File::ReadAllText(string)
    IL_0015:  stloc.0
    IL_0016:  ldarg.0
    IL_0017:  ldfld      class [ClearScript]Microsoft.ClearScript.ScriptEngine TotalTaxation.TaxformCalculationUnitTests.JsRF1013Wrapper::ScriptEngine
    IL_001c:  ldloc.0
    IL_001d:  callvirt   instance void [ClearScript]Microsoft.ClearScript.ScriptEngine::Execute(string)
    IL_0022:  nop
    IL_0023:  nop
    IL_0024:  ret
} // end of method JsRF1013Wrapper::.ctor

我们写了emit代码： ConstructorInfo objCtor = calculatorType.GetConstructor（new Type [] {typeof（ScriptEngine），typeof（string）}）;

Type[] ctorParams = new Type[] { typeof(ScriptEngine), typeof(string) };

ConstructorBuilder wrapperCtor = typeBuilder.DefineConstructor(
               MethodAttributes.Public | 
               MethodAttributes.HideBySig |
               MethodAttributes.SpecialName |
               MethodAttributes.RTSpecialName,
               CallingConventions.Standard, 
               ctorParams);
ILGenerator ctorIL = wrapperCtor.GetILGenerator();

ctorIL.Emit(OpCodes.Ldarg_0);
ctorIL.Emit(OpCodes.Call, objCtor);
ctorIL.Emit(OpCodes.Nop);
ctorIL.Emit(OpCodes.Nop);
ctorIL.Emit(OpCodes.Ldarg_0);
ctorIL.Emit(OpCodes.Ldarg_1);
ctorIL.Emit(OpCodes.Stfld, scriptEngineField);
ctorIL.Emit(OpCodes.Ldarg_2);
ctorIL.Emit(OpCodes.Call, typeof(File).GetMethod("ReadAllText", new Type[] { typeof(string) }));
ctorIL.Emit(OpCodes.Stloc_0);
ctorIL.Emit(OpCodes.Ldarg_0);
ctorIL.Emit(OpCodes.Ldfld, scriptEngineField);
ctorIL.Emit(OpCodes.Ldloc_0);
ctorIL.Emit(OpCodes.Callvirt, typeof(ScriptEngine).GetMethod("Execute", new Type[] { typeof(string) }));
ctorIL.Emit(OpCodes.Nop);
ctorIL.Emit(OpCodes.Nop);
ctorIL.Emit(OpCodes.Stfld, jsFileFullPathField);
ctorIL.Emit(OpCodes.Ret);

并且在使用它时会出现一个名为System.Reflection.TargetInvocationException的异常：

ICalculator calculator = (ICalculator)Activator.CreateInstance(t, new object[] { new JScriptEngine(), jsFileFullPath });

问题是什么？

System.Reflection.TargetInvocationException：动态定义带参数的构造函数

0 个答案: