使用反射发出通用方法会在Invoke处引发异常

I am trying this simple example on creating a generic method using Reflection.Emit but it is causing an exception when calling Invoke and I can't find the problem.

我正在尝试使用Reflection.Emit创建泛型方法的这个简单示例，但它在调用Invoke时导致异常，我找不到问题。

public class Program
{
    public static void Main(string[] args)
    {
        AppDomain appDomain = AppDomain.CurrentDomain;
        AssemblyName name = new AssemblyName("MyAssembly") { Version = new Version("1.0.0.0") };
        AssemblyBuilder ab = appDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.RunAndSave);
        ModuleBuilder mb = ab.DefineDynamicModule("MyModule", "MyAssembly.dll");
        TypeBuilder tb = mb.DefineType("Widget", TypeAttributes.Public);

        // Define a method builder
        MethodBuilder methodBuilder = tb.DefineMethod("MyGenericMethod", MethodAttributes.Public | MethodAttributes.Static);

        // Get generic type parameter builders 
        GenericTypeParameterBuilder[] genericParams =
            methodBuilder.DefineGenericParameters("TKey", "TValue");

        methodBuilder.SetSignature(typeof(int), null, null,
            genericParams,
            null, null);
        methodBuilder.DefineParameter(1, ParameterAttributes.None, "key");
        methodBuilder.DefineParameter(2, ParameterAttributes.None, "val");

        ILGenerator gen = methodBuilder.GetILGenerator();
        MethodInfo writeLineStr = typeof(Console).GetMethod("WriteLine", new[] { typeof(object) });
        gen.Emit(OpCodes.Ldarg_0);
        gen.Emit(OpCodes.Box, genericParams[0]);
        gen.Emit(OpCodes.Call, writeLineStr);
        gen.Emit(OpCodes.Ldarg_1);
        gen.Emit(OpCodes.Box, genericParams[1]);
        gen.Emit(OpCodes.Call, writeLineStr);
        gen.Emit(OpCodes.Ret);

        Type t = tb.CreateType();
        MethodInfo genMeth = t.GetMethod("MyGenericMethod").MakeGenericMethod(typeof(string), typeof(int));
        genMeth.Invoke(null, new object[] { "NumberKey", 100 });
    }
}

When calling genMeth.Invoke, the following exception is thrown

调用genMeth.Invoke时，抛出以下异常

Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the t
arget of an invocation. ---> System.InvalidProgramException: Common Language Runtime detected an inv
alid program.
   at Widget.MyGenericMethod[TKey,TValue](TKey key, TValue val)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Bool
ean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Obje
ct[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder,
 Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at ReflectionEmitDemo14.Program.Main(String[] args) in d:\Projects\ReflectionEmitDemo\ReflectionE
mitDemo14\Program.cs:line 50

1 个解决方案

#1

Your method is static and has two arguments: argument 0 and argument 1. But in the generated IL code you're accessing an argument 2 which does not exist.

您的方法是静态的并且有两个参数：参数0和参数1.但是在生成的IL代码中，您正在访问不存在的参数2。

Another problem is that you're trying to pass an Int32 value to a method that expects a String reference. Box both arguments and pass them to the WriteLine overload that accepts an Object reference.

另一个问题是您尝试将Int32值传递给需要String引用的方法。装入两个参数并将它们传递给接受Object引用的WriteLine重载。

You also have declared your method to return an Int32, but you're not putting anything on the stack before returning.

您还声明了返回Int32的方法，但在返回之前，您没有在堆栈上放置任何内容。

Try to write the method in C# and then take a look at what IL the C# compiler emits (for example, using ILspy). It should look like this:

尝试在C＃中编写该方法，然后查看C＃编译器发出的IL（例如，使用ILspy）。它应该如下所示：

ldarg.0
box !TKey
call void [mscorlib]System.Console::WriteLine(object)

ldarg.1
box !TValue
call void [mscorlib]System.Console::WriteLine(object)

ldc.i4.s 42
ret

#1