Question

I’m having problems proxying metods with parameters using Castle DynamicProxy v1.1.5.0. – I get the exception “Index was outside the bounds of the array.”

If I only use methods with no parameters, OR DynamicProxy v2, everything works ok.
Unfortunately, I’m having trouble convincing the leads on my project to add a dependency to v2 (we’re already using v1 as it comes with NHibernate).

So my question boils down to: can this be done in v1? Am I using it wrong?

Here’s the nitty-gritty.

I’ve implemented a mechanism that simulates inheritance without having compile-time dependencies to the base class. Pleeease don’t ask why, the reasons are ugly 🙁

Here is a complete example showing how this breaks. I’m referencing Castle.DynamicProxy.dll (v1). If I change the references to Castle.DynamicProxy[b]2[/b].dll (+ Castle.Core.dll), un-comment the #define at the beginning of the code.

Sorry for the long-ish code, but I was afraid I might let out some vital detail…
Also: DISCLAIMER: The code sample has some NASTY bugs! (Probably more than I found, too 🙂

//#define DynamicProxyV2

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;


#if DynamicProxyV2
using Castle.Core.Interceptor;
#endif

using Castle.DynamicProxy;

namespace ProxyTest
{

    public interface IMyInterface
    {
        void Foo(object a);
        void Bar(object a);
        void Baz(object a);
    }
    public interface IParam
    {
        string Value { get;}
    }

    public class DefaultImplementation : IMyInterface{
        public virtual void Foo(object a) {
            Console.WriteLine("Default Foo");
            Bar(null);
        }

        public virtual void Bar(object a){
            Baz(null);
        }

        public virtual void Baz(object a){
            Console.WriteLine("Default Baz");
        }
    }

    class DerivedImpl : ProxyDerivedImplementation {
        public DerivedImpl(IMyInterface i_baseImpl)
            : base(i_baseImpl) { }

        public override void Foo(object a) {
            Console.WriteLine("Derived - Foo!");
            base.Bar(null);
        }

        public override void Baz(object a) {
            Console.WriteLine("Derived - Baz!");
        }
    }

    public class DoStuff {
        [STAThread]
        public static void Main()
        {
            Type t = typeof(DefaultImplementation);

            IMyInterface defaultImpl = (IMyInterface)Activator.CreateInstance(t);
            DerivedImpl derived = new DerivedImpl(defaultImpl);
            derived.Foo(null);
        }
    }


    public class ProxyDerivedImplementation : IMyInterface, IInterceptor {
        private IMyInterface m_proxy;
        public ProxyDerivedImplementation(IMyInterface i_defaultImplementation)
        {
            ProxyGenerator pg = new ProxyGenerator();

            Type tt = i_defaultImplementation.GetType();
            m_proxy = (IMyInterface)pg.CreateClassProxy(tt, this);
        }

#if DynamicProxyV2
        #region DynProxy v2
        public void Intercept(IInvocation invocation) {
            try
            {
                MethodInfo i_method = invocation.Method;
                List<Type> types = new List<Type>();

                foreach (ParameterInfo info in i_method.GetParameters())
                {
                    types.Add(info.ParameterType);
                }
                MethodInfo method = this.GetType().GetMethod(i_method.Name, types.ToArray());
                object[] attrs = method.GetCustomAttributes(typeof(NotOverridenAttribute), false);
                if (attrs.Length > 0)
                {
                    invocation.Proceed();
                }
                else
                {
                    invocation.ReturnValue = method.Invoke(this, invocation.Arguments);
                }
            }
            catch (Exception ex)
            {
                Debug.Fail(ex.Message);
                //return null;
            }

        }
        #endregion
#else
        #region DynProxy v1
        public object Intercept(IInvocation i_invocation, params object[] args) {
            try {
                MethodInfo proxiedMethod = i_invocation.Method;
                List<Type> types = new List<Type>();

                foreach (ParameterInfo info in proxiedMethod.GetParameters())
                {
                    types.Add(info.ParameterType);
                }

                //find the corresponding method in the inheritance tree having this class as root
                MethodInfo localMethod = this.GetType().GetMethod(proxiedMethod.Name, types.ToArray());
                object[] attrs = localMethod.GetCustomAttributes(typeof(NotOverridenAttribute), false);
                if (attrs.Length > 0)
                {
                    //it's one of the methods in THIS class, i.e. it's not overridden
                    //-> we can't call the method in this class, because it will re-trigger this intercept
                    //   and we'd get an infinite loop
                    // => just dispatch the method to the original proxied type
                    //
                    return i_invocation.Proceed();
                }
                //else we have an override for this method - call it.
                return localMethod.Invoke(this, args);
            } catch (Exception ex) {
                Debug.Fail(ex.Message);
                return null;
            }
        }
        #endregion
#endif
        [NotOverriden]
        public virtual void Foo(object a) { m_proxy.Foo(a); }

        [NotOverriden]
        public virtual void Bar(object a) { m_proxy.Bar(a); }

        [NotOverriden]
        public virtual void Baz(object a) { m_proxy.Baz(a); }
    }

    class NotOverridenAttribute : Attribute { }

}

Whew! That’s a mouthful.
Here’s the exception that occurs when using v1:

{"Index was outside the bounds of the array."}
    [System.IndexOutOfRangeException]: {"Index was outside the bounds of the array."}
    Data: {System.Collections.ListDictionaryInternal}
    HelpLink: null
    InnerException: null
    Message: "Index was outside the bounds of the array."
    Source: "DynamicAssemblyProxyGen"
    StackTrace: "   at CProxyTypeDefaultImplementationProxyTest0.__delegate_2.Call(Object[] )\r\n   at Castle.DynamicProxy.Invocation.AbstractInvocation.Proceed(Object[] args)\r\n   at ProxyTest.ProxyDerivedImplementation.Intercept(IInvocation i_invocation, Object[] args) in D:\\My Documents\\Visual Studio 2005\\Projects\\DefaultImpl\\AddedValue\\AddedValue.cs:line 133"
    TargetSite: {System.Object Call(System.Object[])}

When running with v2, all I get is the correct output:

Derived – Foo!
Derived – Baz!

…Help?

Answer 1

don’t use old DynamicProxy. It is long unsupported. If you’re using NHibernate that comes with it, I don’t even want to ask which version of NHibernate you’re using. DPv1 is really old