Where to put code in (primarily) windowless WPF app?

Question

So I'm planning on writing an application that is largely a windowless application. There will be windows for user interaction, but only at the request of the user. Otherwise the application sits in the system tray and runs a timer, executing some logic every minute or so. My question is this: As far as I can tell, I would put all the related logic in App.xaml.cs (starting the timer, executing the logic at each interval), but for some reason this seems wrong to me.

The app will have a system tray icon that users can interact with to get details, adjust settings, etc., but otherwise the app just sits there and does what it does. Is it appropriate to put all the code in the code-behind for the App.xaml class? I don't know why, but it seems as if I shouldn't, and there should be somewhere else, but I can't really think of anything.

I've never written an app like this before, hence my ignorance. Any advice would be greatly appreciated. Thanks.

James

Answer 1

Even with applications where most interaction is done through windows it's usually a bad idea to put all the code in the code behind. Interactions are often initiated eventhandlers in the code behind but you can put your code in classes you create yourself.

The same goes for applications that do not show a user interface most of the time. Most of the actions will be initiated from the App.xaml.cs but that doesn't mean all the code has to live there. You can encapsulate timers in their own classes that can kick off other code to do work for example. Divide your code up along lines of responsibilities, a window class does UI stuff, domain logic goes into other files etc. That will enable you to create more maintainable applications.

Answer 2

It doesn't sound like the code belongs there, and at most just a call to start the timers. What does sound like a perfect fit for your issues, is the M-V-VM (Model - View - ViewModel) pattern. As you noteded, it also will 'feel' more correct then attaching logic to your code behind. Using MVVM you can separate your sparse UI into a View, and your code can exist separately in the Model and ViewModel.

I would recomend using the toolkit here, as it also contains good overview documents and a sample you can digest as you create your own solution. Laurent Bugnion has also released a MVVM starter toolkit that you could use to get started.

Also, here is some good stuff to get you started on actually setting up your controls in the system tray.