MS DOS Screen Pop-up

Question

Hello everybody ...

Now I'm creating a C# program and it seems everything is fine ...
My program is a backend service one and so I don't need any interface ...
It takes 10+ seconds to perform its task ...
My problem is ... when I run that program ... the MS-DOS Screen (the black screen with no text at all) is opening until the end of the program ...
Can you pls help me to advise why this happen and how can I prevent it?

Thanks a lot ...
Mg Mg Sa