Wpf datagridcomboboxcolumn question

<Grid>
    <DataGrid x:Name="grid" ItemsSource="{Binding Items}" SelectionChanged="DataGrid_SelectionChanged"/>
</Grid>

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    
        this.DataContext = this;
    
        var list = new List<Data>();
    
        for (int i = 0; i < 10; i++)
        {
           list.Add(new Data() { FirstName = "First " + i, 
                                 LastName = "Last " + i });
        }
    
        this.Items = list;
    }
    
    public IEnumerable Items
    {
        get;
        set;
    }
    
    void DataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
       var selected = grid.SelectedItems;
    }
}

public class Data
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}