BeginAuthenticateAsClient doesn't work in new AppDomain

Question

I am trying to create an SslStream object in a new AppDomain. However, running the BeginAuthenticateAsClient method on the stream causes an Exception to be thrown.

internal class SslWrapper : MarshalByRefObject
{
    public void CreateStream(Stream innerStream)
    {
        var ioStream = new SslStream(innerStream, 
                                     false,
                                     ValidateRemoteCertificate,
                                     SelectLocalCertificate);

        ioStream.BeginAuthenticateAsClient("Target",
                                           GetCertificates(),
                                           SslProtocols.Tls,
                                           false,
                                           new AsyncCallback(CallbackMethod), 
                                           null);
    }

    private void CallbackMethod(IAsyncResult result)
    {
        // TODO: handle callback...
    }
}

The exception states:

The type System.Net.AsyncProtocolRequest in Assembly System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 is not marked as serializable.

Edit: The exception is thrown after calling BeginAuthenticateAsClient(). The SelectLocalCertificate() callback method is called, but ValidateRemoteCertificate() is not.

The new AppDomain and SslWrapper are created as follows:

_appDomain = AppDomain.CreateDomain(name, null, new AppDomainSetup { PrivateBinPath = pathToDll });
_wrapper = (SslWrapper)_appDomain.CreateInstanceFromAndUnwrap(pathToDll, typeof(SslWrapper).FullName);
_wrapper.CreateStream(innerStream);

Using the synchronous AuthenticateAsClient() instead works successfully, as does running the asynchronous code in the default AppDomain.

I assume the exception is related to the AsyncCallback method. However, this method should not be crossing the AppDomain boundary, so why might I be getting the exception? More importantly, is it possible to avoid it?

I am using .NET 2, WinXP 64bit.

Edit: This is also a problem in .NET 4.

Answer 1

the problem should be in your innerStream object, it has to be serializable or MarshalByRefObject in order to work(i.e. be able to be passed as parameter across AppDomain boundary)