This is probably well known, but I just stumbled upon it today.
When building a WinForms app, the output dir (i.e. bin\debug) is recreated, so any blah.exe.config file you may have there is deleted.
To keep your config file - you must add it to the solution, with the name
app.config (not "
", but just app.config)
The build process will rename and copy this config file to the output dir and name it appropriately.