更改SelectedIndex时未选择TabControl标头

Question

First, I found this answer and initially thought it solved my problem: Binding to TabControl SelectedIndex

The screenshots of the tab-header in that post show what I'm seeing with my tabs.

In particular, adding the check if(value != _SelectedTabIndex) before updating the property and raising the PropertyChanged notification seemed to work. By that I mean, it made my first added tab display correctly (with the header also selected).

However, this only works for the first item added to the TabControl. When I add a second item, neither the first or second header is selected, however the second item is visible in the body of the tab, meaning that it sort of works.

Here is my XAML:

<TabControl Grid.Row="1" Grid.Column="2" ItemsSource="{Binding TabViewModels}"
            SelectedIndex="{Binding SelectedTabIndex, Mode=OneWay}">
    <TabControl.ItemContainerStyle>
        <Style TargetType="TabItem">
            <Setter Property="Header" Value="{Binding TabName}" />
            <Setter Property="Content" Value="{Binding}" />
        </Style>
    </TabControl.ItemContainerStyle>
</TabControl>

Here is my CollectionChanged handler:

private void OnTabCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    // Set selected index to last index in collection
    SelectedTabIndex = TabViewModels.Count - 1;
}

And here is my property:

private int _SelectedTabIndex;
public int SelectedTabIndex
{
    get { return _SelectedTabIndex; }
    set
    {
        if(value != _SelectedTabIndex)
        {
            _SelectedTabIndex = value;
            OnPropertyChanged();
        }
    }
}

Answer 1

Okay, so I found what the problem is, but I don't know the best solution. The CollectionChanged event is raised before the TabControl is updated with the new items. This means setting the SelectedTabIndex to the last item is, for a brief moment, out of bounds (until the TabControl's items are updated).

The sequence is like so: 1. Add item to collection 2. CollectionChanged event is raised 3. SelectedTabIndex is set to last item (TabControl doesn't have the recently added item yet) 4. TabControl items are updated

I proved this by creating a Task in the CollectionChanged event handler that delays 10ms, then sets the SelectedTabIndex, but this seems sloppy.