Calling an unmanaged delegate with BeginInvoke

Question

I've a delegate to an unmanaged function on a DLL (which I loaded using GetProcAddress). I can call this delegate with no trouble. When I call the delegates with BeginInvoke, however, I get the following exception:

Managed Debugging Assistant 'FatalExecutionEngineError' has detected a problem in '...'.
Additional Information: The runtime has encountered a fatal error. The address of the 
error was at 0x63fd8687, on thread 0xb4c. The error code is 0xc0000005. This error may
be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common 
sources of this bug include user marshaling errors for COM-interop or PInvoke, which
may corrupt the stack.

This is the code:

        private void OnConnectFinished(IAsyncResult a_oResult)
        {
            ConnectDelegate l_oDelegate = (ConnectDelegate)a_oResult.AsyncState;

            if (ConnectFinished != null)
            {
                ConnectFinished(l_oDelegate.EndInvoke(a_oResult));
            }
        }

        public bool Connect()
        {
            AsyncCallback l_oCallback = new AsyncCallback(OnConnectFinished);
            IAsyncResult l_oResult = DLLConnect.BeginInvoke(l_oCallback, DLLConnect);

                    //This Works!:
            //bool l_bResult = DLLConnect(m_oConnectFinishedDelegate);
            //return l_bResult;

            return true;
        }

Any ideas on why is this happening?

Answer 1

Passing the delegate as userState (the second argument in BeginInvoke ) seems suspicious. Will it work if you pass null there? (Yes, I know that your callback won't work, but this issue can be handled another way. Let's check if the reported error disappears.)