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group:Share CDO Session Among Threads
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thread access only. When the library starts, it initializes COM and doesn't pass the MULTITHREADED flag to CoInitilizeEx. Not necessarily a bug - the code just doesn't support multi-threaded access. -Rob Teixeira [MVP] [quoted text, click to view] "Gary Lee" <glcie@earthlink.net> wrote in message news:z1Luc.16819$Tn6.3669@newsread1.news.pas.earthlink.net... > In VB.NET using CDO, I'd like to allow multiple threads to share a single > MAPI.Session object. If I declare and instantiate sessions within each > thread, I'm OK (although this negates the efficiency I'm looking to add). > But when I declare, e.g., > > Public objSession As MAPI.Session > > I can't access objSession from a worker thread. > > Thanks in advance for any advice. > > Dave James > >
In VB.NET using CDO, I'd like to allow multiple threads to share a single
MAPI.Session object. If I declare and instantiate sessions within each thread, I'm OK (although this negates the efficiency I'm looking to add). But when I declare, e.g., Public objSession As MAPI.Session I can't access objSession from a worker thread. Thanks in advance for any advice. Dave James
Gary,
As Rob suggested, CDO (within .NET) is bound to an STA thread, which means that it can not be used with an MTA thread (it throws an exception if you try). I recently came across the following http://g8.cx/mapi/ "Extended MAPI with C#", which may allow you to use multiple threads (I have not yet tried the above library). Hope this helps Jay [quoted text, click to view] "Gary Lee" <glcie@earthlink.net> wrote in message news:z1Luc.16819$Tn6.3669@newsread1.news.pas.earthlink.net... > In VB.NET using CDO, I'd like to allow multiple threads to share a single > MAPI.Session object. If I declare and instantiate sessions within each > thread, I'm OK (although this negates the efficiency I'm looking to add). > But when I declare, e.g., > > Public objSession As MAPI.Session > > I can't access objSession from a worker thread. > > Thanks in advance for any advice. > > Dave James > >
Thanks Rob and Jay for the replies. I'll check out http://g8.cx/mapi/.
In the meantime, I made things work by creating one session per thread -- not as elegant as I'd like, but it works. [quoted text, click to view] "Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP@msn.com> wrote in message news:eW4ATL5REHA.628@TK2MSFTNGP11.phx.gbl... > Gary, > As Rob suggested, CDO (within .NET) is bound to an STA thread, which means > that it can not be used with an MTA thread (it throws an exception if you > try). > > I recently came across the following http://g8.cx/mapi/ "Extended MAPI with > C#", which may allow you to use multiple threads (I have not yet tried the > above library). > > Hope this helps > Jay > > "Gary Lee" <glcie@earthlink.net> wrote in message > news:z1Luc.16819$Tn6.3669@newsread1.news.pas.earthlink.net... > > In VB.NET using CDO, I'd like to allow multiple threads to share a single > > MAPI.Session object. If I declare and instantiate sessions within each > > thread, I'm OK (although this negates the efficiency I'm looking to add). > > But when I declare, e.g., > > > > Public objSession As MAPI.Session > > > > I can't access objSession from a worker thread. > > > > Thanks in advance for any advice. > > > > Dave James > > > > > >
Sven,
[quoted text, click to view] > I think the explanations for the errors you got might be a bit inaccurate: I'm not certain I've seen a totally accurate explanation yet ;-)[quoted text, click to view] > set the ApartmentState of that thread prior to starting it - I guess that Agreed setting the ApartmentState of a Thread is how you set MTA or STA.> "configures" the call to CoInitialize or CoInitializeEx. If you don't set However my understanding is MAPI (CDO) requires a call to MapiInitialize in addition to CoInitialize. However my limited experimentation & Rob's comments suggests that MapiInitialize is called with STA only. Hence MAPI.Session then throws an exception, as it is attempting to call MapiInitilize with parameters with are incompatible with the previously set ApartmentState... [quoted text, click to view] > JUST A TECHNICAL DEMO, DONT DO THIS IN PRODUCTION CODE: just give it a abletry: > set the ApartmentState property of your thread to MTA and you should be I suspect this will appear to work, I'm concerned what is really happening (no call to CoInitialize or MapiInitialize)... Hope this helps Jay [quoted text, click to view] "Sven Carstensen" <Cven.Sarstensen@moc.tfg> wrote in message news:OdAMnTHSEHA.3056@TK2MSFTNGP11.phx.gbl... > Hi Gary, > > "Gary Lee" <glcie@earthlink.net> wrote in message > news:Gocvc.20232$be.866@newsread2.news.pas.earthlink.net... > > Thanks Rob and Jay for the replies. I'll check out http://g8.cx/mapi/. > > > > In the meantime, I made things work by creating one session per thread -- > > not as elegant as I'd like, but it works. > > that is in many situations the more elegant solution. Whenever you have > threads own the resources they use you get them decoupled which keeps you > away from synchronization problems. > > I think the explanations for the errors you got might be a bit inaccurate: > it is not the COM component CDO which initializes a thread as STA or MTA - > that would not work because you cannot change that setting later on so using > two objects with different apartment models in one thread would result in a > conflict. It is always the client of the COM objects who has to set the > apartment model for each thread it creates. For your main UI thread you can > do this with attributes but for dynamically created threads you will have to > set the ApartmentState of that thread prior to starting it - I guess that > "configures" the call to CoInitialize or CoInitializeEx. If you don't set > that property to STA or MTA COM will not get initialized on that thread. So > any COM call will fail on that thread because of COM not being initialized. > > I think you should even be able to use CDO inproc from an MTA thread. This > should result in a proxy object in the MTA thread which uses thread message > queues to communicate with the real CDO object created in an STA object. > Uups: just looked up my CDO apartment registration: it is set up as "Both" > which means - ahhh come on my developers are clever guys you can use me in > STA or MTA I don't care I always work (well this is a "description" in the > registry of how it should be :) ). So it will even execute directly in the > MTA thread. > > JUST A TECHNICAL DEMO, DONT DO THIS IN PRODUCTION CODE: just give it a try: > set the ApartmentState property of your thread to MTA and you should be able > to use a CDO Session created in one of those in all the others. What will > not work is passing an object reference between STA (your main UI thread > e.g.) and MTA. If you want to do that you will need to marshal the object > reference. CoMarshalInterTreadInterfaceInStream and > CoGetInterfaceAndReleaseStream or use the GIT (global interface table). > > I strongly don't recommend that with CDO because you can run in all kinds of > problems with CDO as it is not really designed as a multithreaded server > library - I ran into so much issues with it just because I wanted to use an > easy COM component instead of ExMapi in a server app :( > > Bye, > SvenC > > > > > > > "Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP@msn.com> wrote in message > > news:eW4ATL5REHA.628@TK2MSFTNGP11.phx.gbl... > > > Gary, > > > As Rob suggested, CDO (within .NET) is bound to an STA thread, which > means > > > that it can not be used with an MTA thread (it throws an exception if > you > > > try). > > > > > > I recently came across the following http://g8.cx/mapi/ "Extended MAPI > > with > > > C#", which may allow you to use multiple threads (I have not yet tried > the > > > above library). > > > > > > Hope this helps > > > Jay > > > > > > "Gary Lee" <glcie@earthlink.net> wrote in message > > > news:z1Luc.16819$Tn6.3669@newsread1.news.pas.earthlink.net... > > > > In VB.NET using CDO, I'd like to allow multiple threads to share a > > single > > > > MAPI.Session object. If I declare and instantiate sessions within > each > > > > thread, I'm OK (although this negates the efficiency I'm looking to > > add). > > > > But when I declare, e.g., > > > > > > > > Public objSession As MAPI.Session > > > > > > > > I can't access objSession from a worker thread. > > > > > > > > Thanks in advance for any advice. > > > > > > > > Dave James > > > > > > > > > > > > > > > > > > > >
Hi Gary,
[quoted text, click to view] "Gary Lee" <glcie@earthlink.net> wrote in message news:Gocvc.20232$be.866@newsread2.news.pas.earthlink.net... > Thanks Rob and Jay for the replies. I'll check out http://g8.cx/mapi/. > > In the meantime, I made things work by creating one session per thread -- > not as elegant as I'd like, but it works. that is in many situations the more elegant solution. Whenever you have threads own the resources they use you get them decoupled which keeps you away from synchronization problems. I think the explanations for the errors you got might be a bit inaccurate: it is not the COM component CDO which initializes a thread as STA or MTA - that would not work because you cannot change that setting later on so using two objects with different apartment models in one thread would result in a conflict. It is always the client of the COM objects who has to set the apartment model for each thread it creates. For your main UI thread you can do this with attributes but for dynamically created threads you will have to set the ApartmentState of that thread prior to starting it - I guess that "configures" the call to CoInitialize or CoInitializeEx. If you don't set that property to STA or MTA COM will not get initialized on that thread. So any COM call will fail on that thread because of COM not being initialized. I think you should even be able to use CDO inproc from an MTA thread. This should result in a proxy object in the MTA thread which uses thread message queues to communicate with the real CDO object created in an STA object. Uups: just looked up my CDO apartment registration: it is set up as "Both" which means - ahhh come on my developers are clever guys you can use me in STA or MTA I don't care I always work (well this is a "description" in the registry of how it should be :) ). So it will even execute directly in the MTA thread. JUST A TECHNICAL DEMO, DONT DO THIS IN PRODUCTION CODE: just give it a try: set the ApartmentState property of your thread to MTA and you should be able to use a CDO Session created in one of those in all the others. What will not work is passing an object reference between STA (your main UI thread e.g.) and MTA. If you want to do that you will need to marshal the object reference. CoMarshalInterTreadInterfaceInStream and CoGetInterfaceAndReleaseStream or use the GIT (global interface table). I strongly don't recommend that with CDO because you can run in all kinds of problems with CDO as it is not really designed as a multithreaded server library - I ran into so much issues with it just because I wanted to use an easy COM component instead of ExMapi in a server app :( Bye, SvenC [quoted text, click to view] > > > "Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP@msn.com> wrote in message > news:eW4ATL5REHA.628@TK2MSFTNGP11.phx.gbl... > > Gary, > > As Rob suggested, CDO (within .NET) is bound to an STA thread, which means > > that it can not be used with an MTA thread (it throws an exception if you > > try). > > > > I recently came across the following http://g8.cx/mapi/ "Extended MAPI > with > > C#", which may allow you to use multiple threads (I have not yet tried the > > above library). > > > > Hope this helps > > Jay > > > > "Gary Lee" <glcie@earthlink.net> wrote in message > > news:z1Luc.16819$Tn6.3669@newsread1.news.pas.earthlink.net... > > > In VB.NET using CDO, I'd like to allow multiple threads to share a > single > > > MAPI.Session object. If I declare and instantiate sessions within each > > > thread, I'm OK (although this negates the efficiency I'm looking to > add). > > > But when I declare, e.g., > > > > > > Public objSession As MAPI.Session > > > > > > I can't access objSession from a worker thread. > > > > > > Thanks in advance for any advice. > > > > > > Dave James > > > > > > > > > > > >
Hi Jay,
[quoted text, click to view] "Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP@msn.com> wrote in message news:e3CBZQKSEHA.1312@TK2MSFTNGP12.phx.gbl... > Sven, > > I think the explanations for the errors you got might be a bit inaccurate: > I'm not certain I've seen a totally accurate explanation yet ;-) one could get the fealing that MS would like to forget about CDO 1.21 all together ;-) [quoted text, click to view] > > set the ApartmentState of that thread prior to starting it - I guess that > > "configures" the call to CoInitialize or CoInitializeEx. If you don't set > Agreed setting the ApartmentState of a Thread is how you set MTA or STA. > > However my understanding is MAPI (CDO) requires a call to MapiInitialize in > addition to CoInitialize. However my limited experimentation & Rob's > comments suggests that MapiInitialize is called with STA only. Hence > MAPI.Session then throws an exception, as it is attempting to call > MapiInitilize with parameters with are incompatible with the previously set > ApartmentState... So true: I forgot MAPIInitialize - one would have to call it with the MAPI_NO_COINIT flag to get it working in an MTA thread. When oh when will we get a good replacment for CDO/ExMAPI with its client side notifications and message file format. Does WebDAV qualify as a candidate for saving messages to files? I like ExMapi when it comes to its internal knowledge to ignore read only or computed properties when I use OpenIMsgOnIStg to copy a message completely to a file based storage. <snip> Bye, SvenC
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