Is there a way to cancel TabControl.Items.CurrentChanging?

Question

There is unfortunately no TabControl.SelectionChanging event (Selector.SelectionChanging), I am struggling to implement this behavior so I can cancel the changing request.

Answer 1

You can also handle the PreviewLostKeyboardFocus event on each TabItem, and set the Handled property of the event arguments to true to prevent switching to another tab:

protected void tabItem_PreviewLostKeyboardFocus(object sender,
    KeyboardFocusChangedEventArgs e)
{
    if (!ValidateTabItem((TabItem) sender)) {
        e.Handled = true;
    }
}

See http://www.netframeworkdev.com/windows-presentation-foundation-wpf/how-to-cancel-navigation-between-tabitems-in-a-tabcontrol-84994.shtml.

Answer 2

I don't know the exact reason why this happens, and it annoys me greatly.

But here's my workaround for it:

In the sample below, checkbox is "locking" the current tab. So checked means user can't change tab.

void Items_CurrentChanging(object sender, CurrentChangingEventArgs e)
{
    if (checkBox1.IsChecked.Value)
    {
        var item = ((ICollectionView)sender).CurrentItem;

        e.Cancel = true;

        tabControl1.SelectedItem = item;
    }
}

Basically, what happens is (if I understand this correctly) the visual tree gets updated, but the logical tree does not. The above way forces the visual to sync with the logical tree.