This is the nicest looking way I've come up with of reading an integer from the app.config. It also sets a default if the configuratation key doesn't exist or isn't an integer.
// Try and find a configured value for this, but if it doesn't exist set it to 30 seconds.
if(!int.TryParse(ConfigurationManager.AppSettings["notificationCheckInterval"], out notificationInterval))
notificationInterval = 30000;