How to Cancel Page Navigation

[Orgbrat]

So I have a Shell application with MVVM and it has a Items list page, NewItem page and a ItemDetail page. If you navigate to the NewItem page, enter some data but forget a field that is required then click Save there is code in the MVVM SaveItem function that pops up a MCT popup and tells the user the field that is required.

The issue is MAUI Shell does not wait for the Popup result but navigates back to the Items list page with the Popup still showing on top and the user has not even clicked his answer in the popup.

My question is how do you cancel the MAUI Shell Navigation process and stay on the NewItem page to correct the missing data?

Orgbrat

[VladislavAntonyuk]

do you have a small repo? I guess you do not await the popup.

[pictos]

If my idea doesn't work, I would reforce the @VladislavAntonyuk 's request for a repo, that way we can take a good look on it

[Orgbrat]

Funny I have basically done what Pictos recommended but without the NavigationService. I added a flag to the application of stopNavigating and then added the OnNavigating overide in AppShell.cs. I set the application level flag from the viewModel and then in that Shell.OnNavigating function I check to see if I am popping the page and stopNavigating is true, if so I cancel the navigation. Then reset stopNavigating flag to false. Works perfectly but there should be a way to cancel a page navigation at the page level.

[pictos]

@Orgbrat I would say that is more about Shell than us. What you're saying makes sense and I believe that you can do it right now using AttachedProperties to control that... Maybe this can be suggested to be implemented in .NET MAUI, do you have in mind how you would like to use it in xaml or C#? Or even how the API should be implemented?

[Orgbrat]

@pictos I do agree with you that this is a Shell issue and not a Toolkit issue. There should be a page event where you could Cancel navigation if some condition was met on the page such as a validation error. But there is no such API available. As you showed me you have to go all the back to the Shell.OnNavigating with a flag value that is application scoped so the method can check the value and know to stop navigation. I may open something in the .NET MAUI repo with this issue.

I thank you and @VladislavAntonyuk for your quick response and effort. You folks are the best... :)

[Orgbrat]

@VladislavAntonyuk As a side note to your statement "I would say you shouldn't initiate the navigation if your validation fails.". In the SaveCommand method if there was page validation issues the code just showed the Popup and then just returned out of the SaveCommand. There was NO navigation initiated because the user needed to fix something on that page. But the Shell was automatically returning to the page that the NewItem page was called from which was what the issue was. Just thought I would share that with you. I have coded a workaround as I stated above. Still Thanks as you were of great assistance.

[CliffAgius]

Closed as answered