[Bug] [UWP] - When calling Navigation.PopAsync inside MasterDetailPage the OnDisappearing is not called

[BrayanKhosravian]

Description

• The first Page is a ContentPage which is wrapped with a NavigationPage
• Inside the first page there is a button which calls navigation.PushAasync and pushes a new MasterDetailPage
• Inside the Master page there is a button which calls Navigation.PopAsync
• After pressing the button the OnDisappearing of the MasterDetailPage is not called The OnDisappearing is actually being called on Android. Didnt tested in for iOS!

Steps to Reproduce

1. clone this repro: https://github.com/Xamarin-Forms-Issues-Repro/MasterDetailUwpOnDisappearing
2. set UWP as startup project
3. set a breakpoint in MasterDetailUwpOnDisappearing.Views.MainPage.OnDisappearing
4. debug the app
5. press the buttton on the first page with the title "Navigate to master detail"
6. on the master page press the red button with the title "navigate back!" => OnDisappearing is not called on UWP

Expected Behavior

OnDisappearing should be called when popping the master detail page from the navigationstack like it is called on android

Actual Behavior

OnDisappearing is not called when popping the masterdetail page from the navigations tack on uwp

Basic Information

• Version with issue: tested with 4.4.0-sr6
• Last known good version: -
• IDE: Visual Studio 2019
• Platform Target Frameworks:
  • UWP: 16299, 17763
• Nuget Packages: this is a modified masterdetail project template from xamarin forms
• Affected Devices: Windows

Screenshots

Reproduction Link

https://github.com/Xamarin-Forms-Issues-Repro/MasterDetailUwpOnDisappearing

Workaround

none

[BrayanKhosravian]

the same applies to modal navigation

[BrayanKhosravian]

FYI @bruzkovsky @gentledepp

[BrayanKhosravian]

i think this issue can be resolved by calling Element.OnDisappearing() in the Xamarin.Forms.Platform.UWP.MasterDetailPageRenderer.Dispose method

public void Dispose()
        {
            ClearMaster();
            ClearDetail();

            Tracker = null;
            if (Element != null)
            {
                Element.SendDisappearing();  // <= Add this
                SetElement(null);
            }
        }

@gentledepp found that out after a search

[BrayanKhosravian]

here is the branch i was working on: https://github.com/BrayanKhosravian/Xamarin.Forms/tree/bug-uwp-10413-ondisappearing-notcalled-after-popasync-in-masterdetail

i already created an issue in the control gallery. you could just pick my commit if that helps. Wasnt able to push the branch to upstream as i dont have premissions.