I made it possible with one single function call to convert an ASE 2 MTS/MTX given the path to the ASE and to the MTX file. It works smooth. The convert function creates a window, shows opens ASE file, publish MTS/MTX and starts looking for messages for the window.

Since I want to be able to call the convertion from another language(C#) I put the convert function into a dll and dll exported that function. I also made 2 other functions, a Initialize function(registering the window class), and a Cleanup function(deleting the BRUSH in the wndClass). This also works to some extent. If I from my c# call the functions like this:

1) Initialize() // registers window class
2) Convert(asefile, mtxfile) // create window, convert file, and start look for messages
3) Cleanup() // delete BRUSH

it also works fine. Then since I want this to be a batch process, I remove the last part of the Convert process, that is start looking for messages. Now I do not recieve messages, and then I get an error. Since I am in another language, I get the error, object not set to an instance, but cannot further specify what it is. What am I doing wrong here? This I want to do, can it be done at all?

Thanks in advance

i am not sure if i understand what the problem is.
you tried to make the application windowless and it doesn't work anymore ?
how do you get the error ?

from C# you can embed some native C++ code. what don't you do that ?