COM Interop throwing EEMessageException when invoking managed DLL

What a nightmare COM interop is proving to me. I have a simple managed DLL containing a WPF window. I have a simple ViewController class that will eventually be launching this window but for now has an empty method that does nothing.

I have created a managed wrapper for this managed DLL, that exposes an interface registered for COM interop. I can call into my managed wrapper OK. I can display a MessageBox in the entry point of my managed wrapper DLL. However, if I attempt to call ANY method on this ViewController class in the DLL I am wrapping, I get this:

First-chance exception at 0x7c812aeb (kernel32.dll) in MfcVSApp1.exe: Microsoft C++ exception: EEMessageException at memory location 0x0012cb30..

It all worked yesterday apparently. Now some code:

My wrapper entities:

[Guid("83C799E0-9808-40c2-A1AB-80BCB77A3B18")]
    [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
    [ComVisible(true)]
    public interface IMaryln
    {
        void GetEphemeris(DateTime date, double latitude, double longitude);

        /// <summary>
        /// 
        /// </summary>
        /// <param name="date"></param>
        /// <param name="latitude"></param>
        /// <param name="longitude"></param>
        void GetEphemeris1(Int64 millSecsSince1970, double latitude, double longitude);
    }

 [Guid("144DB386-D8EF-41a8-B9B1-57EE8A64600C")]
    [ClassInterface(ClassInterfaceType.None)]
    [ProgId("ManagedProxy.Maryln")]
    [ComVisible(true)]
    public class Maryln : IMaryln
    {
        #region IMaryln Members

        public Maryln()
        {
            System.Diagnostics.Debugger.Launch();
        }

        public void GetEphemeris(DateTime date, double latitude, double longitude)
        {
            //new EphemerisViewController().GetEphemeris(date, latitude, longitude);
        }

        public void GetEphemeris1(Int64 nanoSecsSince1970, double latitude, double longitude)
        {
            // This method does not throw.  However, it will not be executed
            // if any method in EphemerisViewController is called.
            MessageBox.Show("Called from c++" + nanoSecsSince1970.ToString());


            try
            {
                //new Maryln().Test();    // this will not throw
                new EphemerisViewController().GetString();   // this will 
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }                              
        }

        public void Test()
        {
            MessageBox.Show("maryln test");
        }

        #endregion
    }

The Managed DLL, referenced by the managed wrapper DLL, contains a UserControl and this ViewController:

public class EphemerisViewController
    {      
        public EphemerisViewController()
        {          
        }                 

        public void GetString()
        {
            MessageBox.Show("me");
        }

    }

This DLL was also registered for COM interop but then开发者_运维百科 I unchecked that option as it did not help matters. Gurus on board, I need help here. This has consumed two working days already and I have taken 3 steps back from where I started. It all worked yesterday.

Addition

The native client is consuming my wrapper as follows:

void CMfcVSApp1Doc::LaunchEphemrisDialog()
{   
    HRESULT hr;
    CoInitialize(NULL);
    try 
    {               
        ManagedProxy::IMarylnPtr maryln(__uuidof(ManagedProxy::Maryln));    
        LONG64 time = 1309897499216000000;
        hr = maryln->GetEphemeris1(time, 0, 0);
    }
    catch(...)
    {

    }
}

Also, I have cleaned and rebuilt solution numerous times but no luck.

---

Do not know what may have happened here but I decided to ditch this wrapper DLL and create a new one from scratch. I did not change the C# project I was wrapping just to see which of these two projects was causing the problem. This act alone somehow allowed me to debug each of the APIs exposed in the C# project being wrapped. Using the project debug technique suggested by Hans P, I was able to further debug my wrapper DLL. I gave a big sigh of relieve just being able to see a managed exception. Definitely a step forward.

It turned out that each call to a wrapped API in EphemerisViewController was throwing a manage exception that a dependency could not be found (located assembly manifest does not match loaded assembly....blah..blah.). We all know what causes this.

After cleaning assembly references thereby eliminating the aforementioned error, I could then call my managed DLL again. A day wasted on one hand. A lot learnt on the other hand. Why the original wrapper stopped working is beyond my comprehension but I am glad to let that go. it have have been a combination of namespace corruption and DLL loading issues but who knows.

I was getting ready to ditch COM interop and dive into MFC but boy, i am glad I stuck to my guns. Compared to C#, C++ development sucks as far as i am concerned. For example just being able to catch a general Exception in C# as apposed to the catch(...) equivalent we have for C++ is a serious benefit. All the crazy c++ syntax and head scratching routines to perform simple conversions make my head spin. Not to mention Intellisense, oh intellisense. With a expired Virtual Assist license that reminds me everyday it is laying dormant, and a tight corporate budget, I will stick to C# for a while maybe with thoughts on investigating C++ libraries like Boost when all of this is done, just in case. But boy, I am happy to get back into .NET.

Lesson learnt here for me is: with COM interop, you have to pay close attention to the details!