Assistance with code

[blazethrower320]

I've been working on an Inventory Application to get some practice with Avalonia. One thing that I have been having trouble with is Bindings, specifically commands. I was able to set up switching pages from the MainViewModel. However struggling with doing it from other pages. For example, from my wasted page to the New Product page. Here is a link to my current project. https://github.com/blazethrower320/InventoryTracker ( Beware your eyes )

Side Note, Right now, most of my code is inside my ViewModelBase since I was able to easily access it by implementing it into other classes. I'm guessing it's supposed to be put into other files?

If possible, would anyone be willing to give me a hand via Discord? If so, my Discord is blazethrower320

[thevortexcloud]

It sounds like you want a router? There is some docs for using the ReactiveUI one here.

https://docs.avaloniaui.net/docs/concepts/reactiveui/routing

But making your own from scratch is fairly simple.

since I was able to easily access it by implementing it into other classes. I'm guessing it's supposed to be put into other files?

Typically you would logically break it up into several view models and views. That way you adhere to single responsibility principle. But it really depends on what you are trying to do and how complicated it is.

If you are also strongly following MVVM, your view models should not contain any application logic. They are just meant to wrap models so the view can bind to them.

[blazethrower320]

Im still a bit confused. Currently MainWindowViewModel holds my pages and current page for the sidebar. I am wanting to add a button for new product. Im guessing I would add a new page command in wasted?

[thevortexcloud]

It depends on what you want to do. If you need it to be possible to make a new product from the side bar at all times then that sounds reasonable to me. The way you could do that with the router would be to instantiate a new instance and then set it as your active page. You can then have buttons/commands on the view for that which save it. But the way I would probably structure an app like this would be:

1. Model layer

   • Create a data access service for loading and saving your items. Where you save/fetch the data from is up to you. For large apps/lots of data I would probably pick some sort of database (EG Sqlite). I would also probably make this an interface/abstract class so I can easily switch between different backends as needed (which can be a very useful thing to do, EG for integration tests).
   • Create various DTO models that abstract away your data access so callers only have to worry about passing around/creating C# objects
   • Depending on how complex your processing is, you probably also want some sort of processing layer in between the data access and your view model. EG to validate product pricing/quantities are correct. That way it will work no matter what data access backend you use and you can also reuse this code outside of the GUI (EG for a command line app).

2. View Model layer

   • Wrap the DTOs with dedicated view models that format everything for display and expose various commands as needed
   • Create a product list view model that holds a list of products. Depending on how many products you have, you probably need to do some lazy loading/paging for this.
   • Create a product view model which directly wraps a DTO product/can be converted into a DTO product.
   • Add a command somewhere to create a new product which sets the view to an editable product view (using the product view model). When the save button is pressed on this, it will update the data access service with the wrapped DTO.

3. View layer

   • Create an edit product view
   • Create a readonly product view
   • Create a product list view
   • Either create a template selector that switches which product view to display based on some flag somewhere, or have a dedicated edit/readonly view model for a product.

This however is more on the "correct" side of MVVM which a lot of people don't bother with.

That said, I don't know enough about your code base to comment on specifics.