mercredi 10 octobre 2018

TargetException in RealProxy Invoke Message for generic type call in a method group

Let's say I have an generic interface IService<T> and a class implementing it Service : IService<Bar> I create a proxy of that interface :

var proxy = new DynamicProxy<IService<Bar>>(new Service()).GetTransparentProxy() as IService<Bar>;

DynamicProxy is a simple implementation of RealProxy :

    public class DynamicProxy<I> : RealProxy
    {
        private I _decorated;

        public DynamicProxy(I decorated) : base(typeof(I))
        {
            this._decorated = decorated;
        }

        public override IMessage Invoke(IMessage msg)
        {
            IMethodCallMessage methodCall = (IMethodCallMessage)msg;
            MethodInfo methodInfo = methodCall.MethodBase as MethodInfo;

            return new ReturnMessage(
                methodInfo.Invoke(this._decorated, methodCall.InArgs),
                null,
                0,
                methodCall.LogicalCallContext,
                methodCall);
        }
    }

When using my proxy directly it works fine :

IEnumerable<Bar> bars = new List<Bar>() { new Bar { id = 2 }, new Bar { id = 3 } };
proxy.Foo(bars.First());

or even with a lambda, it's fine :

 var data = bars.ToList().Select(bar => proxy.Foo(bar)).ToList();

But when used with a method group, it throws a target exception

var data = bars.ToList().Select(proxy.Foo).ToList();

The thrown exception :

{System.Reflection.TargetException: Object does not match target type.
   at System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target)
   at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)

It seems that the realproxy doesn't manage to get the correct type of the generic :

The MethodBase of the IMethodCallMessage is {Int32 Foo(System.__Canon)} instead of {Int32 Foo(Bar)}

Is it a limitation of the method group ? or a bug in the RealProxy implementation ?





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