Comments by bnmc (Top 3 by date)

bnmc 28-Jul-16 10:42am View

Thanks for the reply J. Calhoun; must have missed it.

I think I figured out a good direction to head in, due to replies to my other posted question. The base question here is, should I include the calculation properties in the Model objects, or a wrapper for those Model objects, such as a ViewModel.

I've decided to only bind directly to the ViewModels, so I only create the calculation properties in the ViewModels. But since the ViewModel is acting as a wrapper, and that I want to include totals in the DataGrid in the View, I need to have ObservableCollections of things like TicketsViewModel.ObservableCollection<ticketviewmodel>. Then when a user selects one of those items, the SelectedItem changes which is bound to TicketsViewModel.SelectedTicketViewModel. In TicketsView, there is a UserControl which has it's DataContext set to SelectedTicketViewModel; so it updates every time the user clicks on a different item. Seemed the easiest/best way to do it.

I will look at Observer Pattern again as I think it could make other things a little easier.

bnmc 5-Jul-16 12:55pm View

Thanks for the reply Super Lloyd. It's amazing that this concept isn't discussed much and only seems glossed over. And, the argument from many developers on where to locate some things as it relates to MVVM, makes it more difficult to work this out. Thanks for confirming this is accepted.

I did finally find an article though I hadn't stumbled on before. It discusses just this, about what the responder found confusing. Specifically, "Another kind of object that fits in the ViewModel layer is a wrapper around a Model object that gives it behavior and makes it more usable by a View..." The author goes on to mention about "thick" vs. "thin" ViewModel layers. I strongly suggest reading his response, as it also has a very good explanation.

http://stackoverflow.com/a/5422692/4429864

With your answer and the article I found, I'm going to mark your response as the answer. Thanks for confirming this is an acceptable way to do it!

bnmc 23-May-16 13:41pm View

Thanks for the response Kassim. Your answer provided good insight, and ultimately pushed me in the right direction for the final answer. I don't plan to use any code-behind, so thanks for the reference to "use appropriate command from the view model," otherwise that would have been confusing.

I was still confused though, as what you reference was like what I provided as the XAML I tried already; just not able to figure out how to reference things correctly. I found though that I needed to use "DataContext" in a couple more places to get things to reference correctly. What you show for the header and using DataContext.Column to reference the value directly, gave me the "a-ha" moment. With a little searching, I was able to use elements of what you suggested, examples online, and a little tweaking; to find the final answer. I'll post it as a separate solution, so I can mark up the XAML for easier viewing.