COM Interops on MTA's...

"Daniel Bass" <danREMOVEbass@.blueCAPSbottle.comFIRST> wrote in message
news:OC2INWwwHHA.1164@.TK2MSFTNGP02.phx.gbl...
> Greetings!
> I'm trying to use the SQLXML BulkLoad COM object from a .net multithreaded
> application... I'm currently getting an error when I try to use this
> object saying:
> System.InvalidCastException: Unable to cast COM object of type
> 'SQLXMLBULKLOADLib.SQLXMLBulkLoad4Class' to interface type
> 'SQLXMLBULKLOADLib.ISQLXMLBulkLoad4'. This operation failed because the
> QueryInterface call on the COM component for the interface with IID
> '{88465BA7-AEEE-49A1-9499-4416287A0160}' failed due to the following
> error: No such interface supported (Exception from HRESULT: 0x80004002
> (E_NOINTERFACE)).
> at SQLXMLBULKLOADLib.SQLXMLBulkLoad4Class.set_Connect ionString(String
> pbstrConnectionString)
> at Olympus.Integrate.Client.SqlServerClient.SendMessa ge(String message)
> in C:\Projects\prototype\Integrate\SqlServerClient\Sq lServerClient.vb:line
> 62
> at Olympus.Integrate.Core.Core.MonitorFlow(Object flowObj) in
> C:\Projects\prototype\Integrate\Integrate\Core.vb: line 152
>
> Now I'm guessing that this COM object does support multiple threads.
> So the question is how to get around this. Would wrapping this function in
> a singleton, for example, do the trick? Or maybe having a static function
> in an object?
> What would be the best approach?
> thanks for your time.
> Daniel.
Make sure your thread is initilaize to enter a STA before starting (see
SetApartmentState(ApartmentState.STA) in System.Threading).
Willy.

>
"Daniel Bass" <danREMOVEbass@.blueCAPSbottle.comFIRST> wrote in message
news:e1UxaY5wHHA.1184@.TK2MSFTNGP04.phx.gbl...
> Willy,
> Thanks for your reply.
> In my application I dynamically create multiple threads according to some
> configuration. At this point in the application the knowledge doesn't
> exist as to whether the thread that is created will use the COM object...
> Is it recommended that I just mark each thread as STA?
> For Each myObj As MyObjectType In myObjects
> ' launch a seperate thread for each configured message flow
> Dim t As Thread = New Thread(AddressOf MyThreadStartFunction)
> t.Name = myObj.myName
> t.SetApartmentState(ApartmentState.STA) // <-- ? Is
> this okay ?
> MyThreadHandler.Instance.AddThread(t)
> t.Start(myParameter)
> Next
> Cheers.
> Dan.
>
Dan, The apartment state is a COM only thing, it doesn't affect .NET. An STA
apartment is valid for single and apartment threaded COM object types, so in
your case it is safe to initialize your threads to enter an STA .
Willy.
|||"Daniel Bass" <danREMOVEbass@.blueCAPSbottle.comFIRST> wrote in message
news:OiEYjv7wHHA.3444@.TK2MSFTNGP05.phx.gbl...
> "Willy Denoyette [MVP]" <willy.denoyette@.telenet.be> wrote in message
> news:uj0Wdq7wHHA.4592@.TK2MSFTNGP05.phx.gbl...
> Thanks. I keep getting a ContextSwtichDeadlock, but reading up it sounds
> like a bogus message. My process spends a lot of time looping around in
> other parts of the code while polling which suggests the reason for this
> error coming up.
> Thanks for your help.
> Dan.
>
This is not necessarily bogus message, don't take this too lightly. One
possible reason for the MDA is that your thread fails to pump the message
queue, if that's the case you will have problems whenever the finalizer
needs to release the COM object references you are holding in this thread,
this will block the finalizer thread with as a result that finalizable
objects stay in memory, finally leading into OOM and other kind of failures.
Willy.