Delegate method
Async callback foo
Async callback foo

Unhandled Exception: System.SystemException: Async throws exception

Server stack trace: 
   at foo.async_callback(IAsyncResult ar)
   at System.Runtime.Remoting.Messaging.AsyncResult.SyncProcessMessage(IMessage msg)
   at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink)

Exception rethrown at [0]: 
   at System.Runtime.Remoting.Proxies.RealProxy.EndInvokeHelper(Message reqMsg, Boolean bProxyCase)
   at System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(Object NotUsed, MessageData& msgData)
   at foo_delegate.EndInvoke(IAsyncResult result)
   at foo.Main() 