Reflection.Emit的和泛型类型 [英] Reflection.Emit and generic types

问题描述

我使用 Reflection.Emit的，我想创建一个类型，这将是在C＃中定义以下类型的等效：

I am using Reflection.Emit and I want to create a type that would be the equivalent of the following type defined in C#:

class A
{
    public Tuple<A, int> GetValue(int x)
    {
         return new Tuple<A, int>(this, x);
    }
}

诀窍是，我需要使用泛型类型。从使用我的自定义类型作为一般的参数BCL

The trick is that I need to use a generic type from BCL that uses my custom type as a generic argument.

我用下面的代码片段搞乱：

I'm messing with the following snippet:

var asmName = new AssemblyName("Test");
var access = AssemblyBuilderAccess.Run;
var asm = AppDomain.CurrentDomain.DefineDynamicAssembly(asmName, access);
var module = asm.DefineDynamicModule("Test");

var aType = module.DefineType("A");
var tupleType = typeof(Tuple<,>).MakeGenericType(aType, typeof(int));

var attrs = MethodAttributes.Public;
var method = aType.DefineMethod("GetValue", attrs, tupleType, new [] { typeof(int) });
var gen = method.GetILGenerator();

gen.Emit(OpCodes.Ldarg_0);
gen.Emit(OpCodes.Ldarg_1);

// here is the fail:
var ctor = tupleType.GetConstructor(new [] { typeof(int), aType } );
gen.Emit(OpCodes.Newobj, ctor);

到 GetConstructor 的调用失败，出现以下例外：

The call to GetConstructor fails with the following exception:

NotSupportedException异常：不支持指定的方法。

NotSupportedException: Specified method is not supported.

所以，基本上，它不会让我得到一个类型，仅仅是引用我的自定义类的构造函数，也不我能完成它的发光方法的主体之前的类型。

So, basically, it won't let me get the constructor of a type that merely references my custom type, and neither can I finalize the type before emitting the body of its method.

能否真的不可能走出这个怪圈？

Can it really be impossible to get out of this vicious circle?

推荐答案

由于某些原因，您需要使用 的静态超载GetConstructor（） 来做到这一点。在你的情况，代码看起来是这样的：

For some reason, you need to use the static overload of GetConstructor() to do this. In your case, the code could look like this:

var ctor = TypeBuilder.GetConstructor(
    tupleType, typeof(Tuple<,>).GetConstructors().Single());

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