[wpf] Is there Selected Tab Changed Event in the standard WPF Tab Control

In WPF, is there an event that can be used to determine when a TabControl's selected tab changes?

I have tried using TabControl.SelectionChanged but it is getting fired many times when a child's selection within a tab is changed.

If you set the x:Name property to each TabItem as:

<TabControl x:Name="MyTab" SelectionChanged="TabControl_SelectionChanged">
    <TabItem x:Name="MyTabItem1" Header="One"/>
    <TabItem x:Name="MyTabItem2" Header="2"/>
    <TabItem x:Name="MyTabItem3" Header="Three"/>
</TabControl>

Then you can access to each TabItem at the event:

private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (MyTabItem1.IsSelected)
    // do your stuff
    if (MyTabItem2.IsSelected)
    // do your stuff
    if (MyTabItem3.IsSelected)
    // do your stuff
}

This code seems to work:

    private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        TabItem selectedTab = e.AddedItems[0] as TabItem;  // Gets selected tab

        if (selectedTab.Name == "Tab1")
        {
            // Do work Tab1
        }
        else if (selectedTab.Name == "Tab2")
        {
            // Do work Tab2
        }
    }

If you're using the MVVM pattern then it is inconvenient (and breaks the pattern) to use the event handler. Instead, you can bind each individual TabItem's Selector.IsSelected property to a dependency property in your viewmodel and then handle the PropertyChanged event handler. That way you know exactly which tab was selected/deselected based on the PropertyName and you have a special handler for each tab.

Example: MainView.xaml

<TabControl>
 <TabItem Header="My tab 1" Selector.IsSelected="{Binding IsMyTab1Selected}"> ... </TabItem>
 <TabItem Header="My tab 2" Selector.IsSelected="{Binding IsMyTab2Selected}"> ... </TabItem>
</TabControl>

Example: MainViewModel.cs

public bool IsMyTab1Selected {
 get { return (bool)GetValue(IsMyTab1SelectedProperty); }
 set { SetValue(IsMyTab1SelectedProperty, value); }
}
public static readonly DependencyProperty IsMyTab1SelectedProperty =
DependencyProperty.Register("IsMyTab1Selected", typeof(bool), typeof(MainViewModel), new PropertyMetadata(true, new PropertyChangedCallback(MyPropertyChanged)));

public bool IsMyTab2Selected {
 get { return (bool)GetValue(IsMyTab2SelectedProperty); }
 set { SetValue(IsMyTab2SelectedProperty, value); }
}
public static readonly DependencyProperty IsMyTab2SelectedProperty =
DependencyProperty.Register("IsMyTab2Selected", typeof(bool), typeof(MainViewModel), new PropertyMetadata(false, new PropertyChangedCallback(MyPropertyChanged)));

private void MyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
 if (e.Property.Name == "IsMyTab1Selected") {
  // stuff to do
 } else if (e.Property.Name == "IsMyTab2Selected") {
  // stuff to do
 }
}

If your MainViewModel is INotifyPropertyChanged rather than DependencyObject, then use this instead:

Example: MainViewModel.cs

public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName) {
 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

public MainViewModel() {
 PropertyChanged += handlePropertyChanged;
}

public bool IsMyTab1Selected {
 get { return _IsMyTab1Selected ; }
 set {
  if (value != _IsMyTab1Selected ) {
   _IsMyTab1Selected = value;
   OnPropertyChanged("IsMyTab1Selected ");
  }
 }
}
private bool _IsMyTab1Selected = false;

public bool IsMyTab2Selected {
 get { return _IsMyTab2Selected ; }
 set {
  if (value != _IsMyTab2Selected ) {
   _IsMyTab2Selected = value;
   OnPropertyChanged("IsMyTab2Selected ");
  }
 }
}
private bool _IsMyTab2Selected = false;

private void handlePropertyChanged(object sender, PropertyChangedEventArgs e) {
 if (e.PropertyName == "IsMyTab1Selected") {
  // stuff to do
 } else if (e.PropertyName == "IsMyTab2Selected") {
  // stuff to do
 }
}

That is the correct event. Maybe it's not wired up correctly?

<TabControl SelectionChanged="TabControl_SelectionChanged">
    <TabItem Header="One"/>
    <TabItem Header="2"/>
    <TabItem Header="Three"/>
</TabControl>

in the codebehind....

private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    int i = 34;
}

if I set a breakpoint on the i = 34 line, it ONLY breaks when i change tabs, even when the tabs have child elements and one of them is selected.

You could still use that event. Just check that the sender argument is the control you actually care about and if so, run the event code.

If anyone use WPF Modern UI,they cant use OnTabSelected event.but they can use SelectedSourceChanged event.

like this

<mui:ModernTab Layout="Tab" SelectedSourceChanged="ModernTab_SelectedSourceChanged" Background="Blue" AllowDrop="True" Name="tabcontroller" >

C# code is

private void ModernTab_SelectedSourceChanged(object sender, SourceEventArgs e)
    {
          var links = ((ModernTab)sender).Links;

          var link = this.tabcontroller.Links.FirstOrDefault(l => l.Source == e.Source);

          if (link != null) {
              var index = this.tabcontroller.Links.IndexOf(link);
              MessageBox.Show(index.ToString());
          }            
    }

The event generated is bubbling up until it is handled.

This xaml portion below triggers ui_Tab_Changed after ui_A_Changed when the item selected in the ListView changes, regardless of TabItem change in the TabControl.

<TabControl SelectionChanged="ui_Tab_Changed">
  <TabItem>
    <ListView SelectionChanged="ui_A_Changed" />
  </TabItem>
  <TabItem>
    <ListView SelectionChanged="ui_B_Changed" />
  </TabItem>
</TabControl>

We need to consume the event in ui_A_Changed (and ui_B_Changed, and so on):

private void ui_A_Changed(object sender, SelectionChangedEventArgs e) {
  // do what you need to do
  ...
  // then consume the event
  e.Handled = true;
}

If you just want to have an event when a tab is selected, this is the correct way:

<TabControl>
    <TabItem Selector.Selected="OnTabSelected" />
    <TabItem Selector.Selected="OnTabSelected" />
    <TabItem Selector.Selected="OnTabSelected" />
    <!-- You can also catch the unselected event -->
    <TabItem Selector.Unselected="OnTabUnSelected" />
</TabControl>

And in your code

    private void OnTabSelected(object sender, RoutedEventArgs e)
    {
        var tab = sender as TabItem;
        if (tab != null)
        {
            // this tab is selected!
        }
    }