Thank you for your reply.
When I launch the executable, only the "searching"/"waiting" cursor of windows is displayed. Then after about 20 seconds my application shows up. The EXE file is only 16 Ko !!
The interesting thing is that, when I launch it within the Visual Studio environment, this does not happen and it launches instantly.
Indeed, since it is a simple blank program, my application is not signed. Do you think this could avoid Avast to act like this ?
However, it happends everytime I launch the application, even if i start it 10 times in a row, Avast will still analyze it every time ...