如何从 TabControl 获取以前选择的 TabItem 索引？

Question

Following xaml code for your testing needs.

<Window x:Class="MainWindow"  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="200" Width="350">
<DockPanel>
    <TabControl x:Name="TabControl" DockPanel.Dock="top">
        <TabItem x:Name="TabItem1" Header="London">
            <Label Content="London" />
        </TabItem>
        <TabItem x:Name="TabItem2" Header="Paris">
            <Label Content="Paris" />
        </TabItem>
        <TabItem x:Name="TabItem3" Header="Tokyo">
            <Label Content="Tokyo" />
        </TabItem>
        <TabItem x:Name="TabItem4" Header="Istanbul">
            <Label Content="Istanbul" />
        </TabItem>
    </TabControl>
</DockPanel>
</Window>

How to get previous TabItem Index from TabControl and show in the MessageBox?

I need vb.net code running from code behind.

Answer 1

RemovedItems is an IList property in the SelectionChangedEventArgs that holds the items that were unselected since the last time the SelectionChanged event occurred. You could check it each time the SelectionChanged of the TabControl event occurred:

private void TabControl_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (e.RemovedItems.Count > 0)
        {
            var oldTabItem = e.RemovedItems[0] as TabItem;
        }
    }

xaml:

 <DockPanel>
        <TabControl x:Name="TabControl" DockPanel.Dock="top" SelectionChanged="TabControl_OnSelectionChanged" > ..