public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); List list = new List(); list.Add(new City { ID = 1, Name = "City1" }); list.Add(new City { ID = 2, Name = "City2" }); list.Add(new City { ID = 3, Name = "City3" }); MyCombobox1.ItemsSource = list; MyCombobox1.SelectedIndex = 0; MyCombobox2.ItemsSource = list; MyCombobox2.SelectedIndex = 0; } private void HandleCheck(object sender, RoutedEventArgs e) { this.MyCombobox1.FlowDirection = FlowDirection.LeftToRight; this.MyCombobox2.FlowDirection = FlowDirection.RightToLeft; } private void HandleUnchecked(object sender, RoutedEventArgs e) { this.MyCombobox1.FlowDirection = FlowDirection.RightToLeft; this.MyCombobox2.FlowDirection = FlowDirection.LeftToRight; } } public class City { public int ID { get; set; } public string Name { get; set; } }