.NET remoting exception: Permission denied: cannot call non-public or static methods remotely

Question

I'm writing a program which will allow to load a specific managed .DLL file and play with it. Since I want the ability to unload the .DLL file, I'm creating two AppDomains - one for the app itself, the other for the currently loaded .DLL.

Since most of the objects in the loaded .DLL do not serialize well, I'm creating a MarshalByRefObject wrapper class which will keep the object itself in its own AppDomain, and expose some reflection functions to the main application AppDomain.

However when I try to invoke a method on the remote object I get stuck with an exception:

Permission denied: cannot call non-public or static methods remotely.

This is very strange, because I'm not using any non-public or static methods at all. In essence, what I have is:

class RemoteObjectWrapper: MarshalByRefObject
{
    private Type SourceType;
    private object Source;

    public RemoteObjectWrapper(object source)
    {
        if (source == null)
            throw new ArgumentNullException("source");
        this.Source = source;
        this.SourceType = source.GetType();
    }
    public T WrapValue<T>(object value)
    {
        if ( value == null )
            return default(T);
        var TType = typeof(T);
        if (TType == typeof(RemoteObjectWrapper))
            value = new RemoteObjectWrapper(value);
        return (T)value;
    }
    public T InvokeMethod<T>(string methodName, params object[] args)
    {
        return WrapValue<T>(SourceType.InvokeMember(methodName,
            System.Reflection.BindingFlags.FlattenHierarchy | System.Reflection.BindingFlags.Instance |
            System.Reflection.BindingFlags.InvokeMethod | System.Reflection.BindingFlags.Public, null, this.Source, args));

    }
}

And I get the exception when I try to do:

var c = SomeInstanceOfRemoteObjectWrapper.InvokeMethod<RemoteObjectWrapper>("somePublicMethod", "some string parameter");

What's going on here? As far as I can understand, the InvokeMethod method doesn't even get executed, the exception is thrown when I try to run it.

Added: To clarify - SomeInstanceOfRemoteObjectWrapper is constructed in the .DLL's AppDomain and then returned to my main AppDomain, The InvokeMethod<T>() is called from my main AppDomain (and I expect it to execute in the .DLL's AppDomain).

Answer 1

Even the method InvokeMethod<T> is public it is contained within an internal class. No modifier in C# makes it internal. Hence the effective visibility of InvokeMethod<T> is internal and you are getting the exception. Making RemoteObjectWrapper public should fix this problem.