Removing ViewModels in Prism when Closing Window

Question

I have a winform application with data grid rows with some icons. When the user clicks on one of the icons, a WPF window opens. I have created this WPF window using Prism i.e. it has shell and regions mapped to view.

The issues I am facing is: When I tried to close the WPF window, I get the exception "Cannot set Visibility or call Show, ShowDialog, or WindowInteropHelper.EnsureHandle after a Window has closed." I understand that we can resolve the issue by hiding the window instead of closing it. However, this makes my ViewModel and Services representing the older WPF window. I have kept the static counter in the ViewModels and observed that every time, I open the WPF window, static count increases which means my old view models are not getting destroyed.

I would like how to handle this scenario correctly so that when I close the window everything related to the window should be disposed off. I tried to do container.dispose in ShellViewModel, however, still it did not work.

you could use the new IDialogService that Prism offers github.com/PrismLibrary/Prism/pull/1682 — Luca
I think IDialogService is mainly used to replace MessageBox use cases. In my case, I have a pretty complex UI on the WPF with 3 regions in a shell. — Scorp
You can combine the IDialogService using your own ViewModel, Regions etc and use a scoped region manager. Otherwise you would need to create a ShellService --> There is an answer for that already: stackoverflow.com/questions/33010756/… — Luca

Haukinger Haukinger · Accepted Answer · 2019-11-25T07:23:33

There are two aspects here. Firstly, you can use either RegionMemberLifetimeAttribute on your view model or implement IRegionMemberLifetime to make Prism create a new instance each time.

Secondly, you have to create your own RegionBehavior (or take it from this Github Issue) to make Prism dispose view models.

Removing ViewModels in Prism when Closing Window

1 Answers