WPF SelectedIndex set issue of TabControl

问题

I have a TabControl with two items.

<TabControl x:Name="tab" SelectionChanged="TabControl_SelectionChanged">
    <TabItem Header="TabItem1">
    <Grid />
</TabItem>
<TabItem Header="TabItem2">
    <Grid />
</TabItem>
</TabControl>

private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    Debug.WriteLine("Selected Index: " + tab.SelectedIndex);

    if (tab.SelectedIndex == 1)
    {
        tab.SelectedIndex = 0;
    }
}

when click 2nd item, 1st item have focus and print below.

Selected Index: 1
Selected Index: 0

but retry clicking 2nd item, no output! SelectionChanged event do not fire.

what's wrong? Is there work around?

回答1:

This is because you are changing the selectedIndex within the SelcetedIndexChanged event which will call itself in sycnhronous manner. Instead try to put it on UI dispatcher in an aysnchronous manner like this -

private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
   Debug.WriteLine("Selected Index: " + tab.SelectedIndex);

   if (tab.SelectedIndex == 1)
   {
      Application.Current.Dispatcher.BeginInvoke
          ((Action)delegate { tab.SelectedIndex = 0; }, DispatcherPriority.Render, null);
   }
}

It will give you the desired output.

回答2:

If you click the tab that is already selected, there is no selection change now is there?
So the SelectionChanged event won't fire.

You would have to hook an event handler on the Click event of the Header of the TabItem

来源：https://stackoverflow.com/questions/7786300/wpf-selectedindex-set-issue-of-tabcontrol