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.NET Forum / .NET Framework / Interop / September 2005.NET events do not execute on primary thread
My .NET application handles events from an out-of-proc COM server. These events do not execute on the app's primary thread, however. Is this a consequence of COM Interop or can this be controlled? (The .NET app is configured to run in a STA.) In a VB6 program, the events are executed on the primary thread. Thanks for the help. This is one major difference between VB6 and .NET. In VB6 all of the objects you create are STA COM objects. This is what caused the events to be marshaled back to the primary thread. .NET objects have no concept of thread affinitiy [1]. The best way to view a .NET object is that it is a MTA object that aggregates the free threaded marshaller, (or that it lives in the thread nuetral apartment). You will have to manually Marshal these events back to the foreground thread. [1] Technically ContextBound objects do have a concept of thread affinity but that's not relevant in this scenario.  SignatureJared Parsons [MSFT] jaredpar@online.microsoft.com http://blogs.msdn.com/jaredpar "This posting is provided "AS IS" with no warranties, and confers no rights" > My .NET application handles events from an out-of-proc COM server. These > events do not execute on the app's primary thread, however. Is this a > consequence of COM Interop or can this be controlled? (The .NET app is > configured to run in a STA.) In a VB6 program, the events are executed on > the primary thread. Thanks for the help. Thanks for the explanation. Switching to the primary thread to handle the event solved the original problem, which was slow execution on in-proc, apartment-threaded COM server methods. (Roughly 80 times faster on the primary thread!) Thinking that cross-apartment marshaling was responsible, I changed the in-proc server to the free-threaded model, but the timings didn't improve. Was cross-apartment marshaling a bad theory or is .NET/COM Interop somehow affecting this? Thanks again for the help. > This is one major difference between VB6 and .NET. In VB6 all of the > objects you create are STA COM objects. This is what caused the events to [quoted text clipped - 15 lines] >> on >> the primary thread. Thanks for the help. Hi George, I think cross-apartment marshaling was to provide the ability to do COM call when they lives in the different apartment. So cross-apartment do will have some performance hit, but that is necessary when we have to do cross-apartment marshaling, because the COM call between apartments is common. We can not make sure all the COM call occur on the same thread, that will limit the COM's ability. Also the .NET Interop will also need some more effort to do the COM/.NET type converting and parameter passing.... Best regards, Peter Huang Microsoft Online Partner Support SignatureGet Secure! - www.microsoft.com/security This posting is provided "AS IS" with no warranties, and confers no rights. I'm missing something here, you are talking about an out-proc COM server, in this scenario there is no cross-apartment marshaling involved, all there is is cross-process marshaling over DCOM which is allways much slower than in-proc marshaling between incompatible apartments. Question is what out-proc server are you talking about? Is this a VB6 ActiveX server? Willy. > Thanks for the explanation. Switching to the primary thread to handle the > event solved the original problem, which was slow execution on in-proc, [quoted text clipped - 26 lines] >>> on >>> the primary thread. Thanks for the help. In handling a COM event from the out-of-proc server, the app calls a method on an in-proc server. This method executes more slowly when called from the event handler than it does if called from the app's primary thread. I suspected marshaling was responsible since the event handler thread (affiliated with an MTA) was using a COM object created in a STA. Creating the in-proc COM object in an MTA however, did not improve performance. > I'm missing something here, you are talking about an out-proc COM server, > in this scenario there is no cross-apartment marshaling involved, all [quoted text clipped - 35 lines] >>>> on >>>> the primary thread. Thanks for the help. Hello George, I am reviewing the issue thread. Do you still have more concerns on it? If there is any question, please feel free to post here and we will follow up. Thanks very much. Best regards, Yanhong Huang Microsoft Community Support Get Secure! ¨C www.microsoft.com/security Register to Access MSDN Managed Newsgroups! -http://support.microsoft.com/default.aspx?scid=/servicedesks/msdn/nospam.as p&SD=msdn This posting is provided "AS IS" with no warranties, and confers no rights. Hi Yanhong Huang, Thanks for checking. We have opened a case with Microsoft Support on this and are awaiting further information. George > Hello George, > [quoted text clipped - 15 lines] > This posting is provided "AS IS" with no warranties, and confers no > rights. Hi Thanks for your updated! Best regards, Peter Huang Microsoft Online Partner Support SignatureGet Secure! - www.microsoft.com/security This posting is provided "AS IS" with no warranties, and confers no rights. Hi George, Thanks very much for your update. If it is convenient for you, could you please update the community with the result after you communicate with support team? Hopefully the community can benefit from it. Thanks again for participating the community. Have a nice day. Best regards, Yanhong Huang Microsoft Community Support Get Secure! ¨C www.microsoft.com/security Register to Access MSDN Managed Newsgroups! -http://support.microsoft.com/default.aspx?scid=/servicedesks/msdn/nospam.as p&SD=msdn This posting is provided "AS IS" with no warranties, and confers no rights. 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