How to know the last two TabItems which I selected in a TabControl in WPF?

Question

I have a WPF application where I need to use Tab Control. In my Tab Control I have total four tab items. I need to know the last two tab items which I selected.

Here my MainWindow.xaml code :

 <Grid>
             <Grid.RowDefinitions>
                 <RowDefinition Height="*"/>
                 <RowDefinition Height="50"/>
             </Grid.RowDefinitions>

                         Grid.Row="0" 
                         x:Name="TestTabs">
                 <TabItem Header="News"/>
                 <TabItem Header="DLC"/>
                 <TabItem Header="Mods"/>
                 <TabItem Header="Settings"/>

     </TabControl>
         </Grid>

I can easily figure out the tab item which is currently selected through <DataTrigger Binding="{Binding ElementName=TestTabs, Path=SelectedIndex}" Value="1"> that means through SelectedIndex property But I don't know How to track the last and previous tab items which I selected.

I know that I have to do this through a ViewModel But I don't know how I can do that and How I bound to tab control data context.

Answer 1

For getting the last two SelectedTabItem of the TabControl, you could try to combine the following method into your code
MainWindow.xaml:

<Window.Resources>  
        <local:TestViewModel x:Key="MainViewModel"/>  
    </Window.Resources>  
    <Grid>  
        <Grid.RowDefinitions>  
            <RowDefinition Height="*"/>  
            <RowDefinition Height="50"/>  
        </Grid.RowDefinitions>  
        <TabControl DataContext="{StaticResource MainViewModel}"   
                    SelectedIndex="{Binding Selected}"   
                    Grid.Row="0"   
                    x:Name="TestTabs">  
            <TabItem Header="Section 1"/>  
            <TabItem Header="Section 2"/>  
            <TabItem Header="Section 3"/>  
        </TabControl>  
        <Button Content="Check   
                Selected Index"   
                Grid.Row="1"   
                x:Name="TestButton"   
                Click="TestButton_OnClick"/>  
    </Grid>  

MainWindow.xaml.cs:

using System.ComponentModel;  
using System.Windows;  
  
namespace TabControlPreviousSelected  
{  
  public partial class MainWindow : Window  
  {  
    public MainWindow()  
    {  
      InitializeComponent();  
    }  
    private void TestButton_OnClick(object sender, RoutedEventArgs e)  
    {  
      var vm = TestTabs.DataContext as TestViewModel;  
      MessageBox.Show(string.Format("You selected tab {0} ,previous selected tab{1}", vm.Selected,vm.PreviousSelected));  
    }  
  }  
  class TestViewModel : INotifyPropertyChanged  
  {  
    private int _selected;  
    public int Selected  
    {  
      get { return _selected; }  
      set  
      {  
        int temp=_selected;  
        _selected = value;  
        _previousSelected = temp;  
        NotifyPropertyChanged("Selected",temp,value);  
        NotifyPropertyChanged("PreviousSelected", temp, temp);  
      }  
    }  
    int _previousSelected=0;  
    public int PreviousSelected  
    {  
      get {  return _previousSelected; }  
       
    }  
    public event PropertyChangedEventHandler PropertyChanged;  
    protected void NotifyPropertyChanged<T>(string propertyName, T oldvalue, T newvalue)  
    {  
      OnPropertyChanged(this, new PropertyChangedExtendedEventArgs<T>(propertyName, oldvalue, newvalue));  
    }  
    public virtual void OnPropertyChanged(object sender, PropertyChangedEventArgs e)  
    {  
      PropertyChangedEventHandler handler = PropertyChanged;  
      if (handler != null)  
        handler(sender, e);  
    }  
  }  
  public class PropertyChangedExtendedEventArgs<T> : PropertyChangedEventArgs  
  {  
    public virtual T OldValue { get; private set; }  
    public virtual T NewValue { get; private set; }  
  
    public PropertyChangedExtendedEventArgs(string propertyName, T oldValue, T newValue)  
        : base(propertyName)  
    {  
      OldValue = oldValue;  
      NewValue = newValue;  
    }  
  }  
}  

The result:

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