[Bug] TabView SelectedIndex Binding does not work

[acaliaro]

Description

                <xct:TabView
                    BackgroundColor="White"
                    SelectedIndex="{Binding SelectedTabViewIndex}"
                    SelectionChanged="TabView_SelectionChanged">

I have a TabView with 2 TabViewItem. I set a SelectedTabViewIndex binding with SelectedIndex, and SelectionChanged event.

I see that TabView_SelectionChanged is called and NewValue and OldValue change, but SelectedTabViewIndex is always 1:

[0:] MainPage: TabView_SelectionChanged new: 1 - old: 0
[0:] MainPage: TabView_SelectionChanged: SelectedTabViewIndex: 1
[0:] MainPage: TabView_SelectionChanged new: 0 - old: 1
[0:] MainPage: TabView_SelectionChanged: SelectedTabViewIndex: 1

Steps to Reproduce

See the attached repo

Expected Behavior

SelectedIndex binding should change the binded value

Actual Behavior

Binded value does not change

Basic Information

• Version with issue: 1.1.0-preview1009
• Last known good version: unknown
• IDE: Visual Studio 2019 16.8.4
• Platform Target Frameworks:
  • iOS:
  • Android: 10
  • UWP:
• Android Support Library Version:
• Nuget Packages:
• Affected Devices:

Workaround

Reproduction imagery

Reproduction Link

TestFody.zip

[Cfun1]

@acaliaro I have briefly tested your repo, I believe that the reason have to do with raising INotifyPropertyChnaged and setting/updating on your SelectedTabViewIndex property in your StudentViewModel.cs that why it is always with the default initial value that you gave it (1), could you please confirm if it is the case ?

[acaliaro]

@acaliaro I have briefly tested your repo, I believe that the reason have to do with raising INotifyPropertyChnaged and setting/updating on your SelectedTabViewIndex property in your StudentViewModel.cs that why it is always with the default initial value that you gave it (1), could you please confirm if it is the case ?

@Cfun1 it should be raised automatically because of PropertyChanged.Fody, but I take a look

[acaliaro]

it semms that with

SelectedIndex="{Binding SelectedTabViewIndex, Mode=TwoWay}"

it works

[AndreiMisiukevich]

@jsuarezruiz is it a bug and SelectedIndexProperty should have TwoWay binding mode by default?