Debugger doesn"t stop at break points

I have an executable "ProcessController.exe" that's Windows service.
It runs in the background as a service.

It depends on "Distribution.dll" that's in the same folder. Now I want
to debug the "Distribution" project whose output is
"Distribution.dll".

If I start the service, and then go to the "Distribution" project to
attach the process of "ProcessController.exe", it won't get to any
break point I've set.

What's the procedure of setting up the debugging environment?

Thanks!