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.NET Forum / .NET Framework / Interop / June 2005Calling a COM object from a different thread
Hello, I have the following simple Architecture: Server in CSharp <===> COM DLL (Apartment threading) <====> DB When I start the server I need to load several COM objects from the DB. This lasts between 5 and 10 minutes. I would like to do this in a worker thread to prevent the server to hang. So I think that I should: - Create my objects in my main STA thread (should I change that to MTA instead ???) - Marshal the interfaces into another thread (MTA) - Call the DB Load method from this worker thread. The issue is that I have absolutely no idea whether it is the correct way to do it in .Net and if it is on how to do it in CSharp! Can anyone help please with an example? Alternatively here are a few questions: - How do I marshal the COM interface (do I need to do it through unsafe code?) - How do I create a worker MTA thread? - Can the main application thread be an MTA instead of an STA (there is a GUI)? Many thanks in advance for any help.  Signature---- http://michael.moreno.free.fr/ > Hello, > [quoted text clipped - 26 lines] > > Many thanks in advance for any help. No, you should never init a UI thread for MTA, nor should you create instances of STA objects on MTA threads. All you have to do is create a background thread and initialize it to enter a STA before you start the thread. After that you simply create an instance of the COM object and call your methods on it. Thread t = new Thread(..... t.ApartmentState = ApartmentState.STA; t.IsBackground = true; t.Start(); Just take care when updating the UI from this thread, you have to use Control.Invoke or Control.BeginInvoke to do so. Willy. > No, you should never init a UI thread for MTA, nor should you create > instances of STA objects on MTA threads. OK, thanks > All you have to do is create a background thread and initialize it to enter a > STA before you start the thread. After that you simply create an instance of [quoted text clipped - 4 lines] > t.IsBackground = true; > t.Start(); Thank you. Do you really mean that from this thread I can access my COM object that were created in the main thread without having to marshall the interface? > Just take care when updating the UI from this thread, you have to use > Control.Invoke or Control.BeginInvoke to do so. Yes thanks. Signature---- http://michael.moreno.free.fr/ Inline ** Willy. >> No, you should never init a UI thread for MTA, nor should you create >> instances of STA objects on MTA threads. [quoted text clipped - 13 lines] > object that were created in the main thread without having to marshall the > interface? ** Yes you can, but that doesn't mean you should create the object on the Main UI thread, if you only intend to call methods from the background thread you better create the COM object on this thead. If you are calling methods on both you can create an instance on both as well, so each will have his own instance, no marshaling needed. If however, you create an instance on the Main thread and pass a reference to it to the background thread, the CLR will automagically marshall the Interface pointer for you (tout gratuit). >> Just take care when updating the UI from this thread, you have to use >> Control.Invoke or Control.BeginInvoke to do so. > > Yes thanks. > ** Yes you can, but that doesn't mean you should create the object on the > Main UI thread, if you only intend to call methods from the background thread > you better create the COM object on this thead. yes I agree. > If however, you create an instance on the Main thread and pass a reference to > it to the background thread, the CLR will automagically marshall the > Interface pointer for you (tout gratuit). That is the best news I have heard for a long time!!!! Thanks a lot for your help. Signature---- http://michael.moreno.free.fr/
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