How to obtain the SelectionChanged event on a DataGrid using ItemsControl within the MVVM pattern?

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To obtain the SelectionChanged event on a DataGrid using ItemsControl within the MVVM pattern, you can follow these steps:

1. Create a DataGrid control in your view as usual.
2. Bind the ItemsSource property of the DataGrid to a collection property in your ViewModel.
3. Add a SelectedItem property to your ViewModel and bind it to the SelectedItem property of the DataGrid.
4. Create a Command in your ViewModel that will handle the SelectionChanged event.
5. Attach the Command to the PreviewMouseLeftButtonDown event of the DataGrid using an EventTrigger.
6. In the CommandHandler, set the SelectedItem property to the newly selected item.

Here's an example XAML code snippet:

<DataGrid ItemsSource="{Binding MyItems}"
          SelectedItem="{Binding SelectedItem}">
  <i:Interaction.Triggers>
    <i:EventTrigger EventName="PreviewMouseLeftButtonDown">
      <i:InvokeCommandAction Command="{Binding SelectionChangedCommand}" />
    </i:EventTrigger>
  </i:Interaction.Triggers>
</DataGrid>

In the ViewModel, you can define the properties and command like this:

private ObservableCollection<MyItem> _myItems;
public ObservableCollection<MyItem> MyItems
{
  get { return _myItems; }
  set { _myItems = value; OnPropertyChanged(nameof(MyItems)); }
}

private MyItem _selectedItem;
public MyItem SelectedItem
{
  get { return _selectedItem; }
  set { _selectedItem = value; OnPropertyChanged(nameof(SelectedItem)); }
}

public ICommand SelectionChangedCommand => new RelayCommand(SelectionChangedHandler);

private void SelectionChangedHandler()
{
  // Do something with the SelectedItem property
}

This approach allows you to handle the SelectionChanged event using the MVVM pattern and maintain separation of concerns between the view and the ViewModel.