DLL-call and API-call from DLL that is called by TestStand

[mbrost]

I've a rather complicated problem:
I've written a DLL (Visual C++) that is used by TestStand. This DLL (call it a.dll) gets its settings by calling another DLL (call it b.dll) which reads those settings from a database. This works fine, but a.dll uses a third party product (Altia Design) via an api. If I start a sequence which now calls a.dll the api-calls don't seem to work. I've written a little test application which is calling the same dll-functions and it works prefectly. All settings that are obtained via the b.dll are correct (checked it with the VC++ debugger).
Now some strange behavior: If I use the Edit function of my teststep, which calls the a.dll, and then start the sequence again it works. I can't fig
ure out where the problem is. All settings are in the database and are never part of teststand. Does my teststep which calls a.dll need to be changed? I think the problem is with teststand since the whole mechanism works fine with my test application.

[James_Grey]

It might be that the Altia Design component needs to be called from a Single-Threaded Apartment. To test this, place the step that calls your DLL in a subsequence. In the call to the subsequence, select Multithreading and Remote Execution>>Run Sequence in a New Thread. Then click Settings... and checkmark Use Single-Threaded Apartment. To wait for your subsequence to complete and to retrieve its results, insert a Synchronization>>Wait step after the sequence call step, configure it to Wait for Thread, and select your sequence call step from the ring.

BTW, what errors are you getting?

[mbrost]

I tried your suggestions but unfortunately they didn't work. Are there any other ways to call a DLL function? Is there some in depth documentation about the DLL-Adapter and the way TestStand uses it? (I remember having some trouble calling a DLL that used an ActiveX -Control)
I get a user defined error code. The function that starts Altia returns zero, which means it didn't work. Not much information there I admit ;-( I tried to call the Altia function repeatedly with a break (2000ms) between each call but it didn't work)