For Windows Forms projects, you can start your deployed application
from its executable file before starting the debugger, and then
attach to the running process from the debugger.

1. In the Project painter, select Run > Attach to .NET Process.
2. In the dialog box that opens, select the process you want to attach to.
   After you attach to the process, it starts running in the
   debugger and you can set breakpoints as you normally do.

Select
Run > Detach to detach from the process. This gives you more flexibility
than simply using just-in-time (JIT) debugging.