WPF ComboBox - Simple and Effective Editable Control

<syncfusion:ComboBoxAdv Height="30" Width="200" 
                              HorizontalAlignment="Center"  
                              VerticalAlignment="Center" > 
            <syncfusion:ComboBoxItemAdv Content="Denmark" /> 
            <syncfusion:ComboBoxItemAdv Content="New Zealand" /> 
            <syncfusion:ComboBoxItemAdv Content="Canada" /> 
            <syncfusion:ComboBoxItemAdv Content="Russia" /> 
            <syncfusion:ComboBoxItemAdv Content="Japan" /> 
        </syncfusion:ComboBoxAdv>

public partial class MainWindow : Window 
{ 
    public MainWindow() 
    { 
        InitializeComponent(); 
                  ComboBoxAdv comboBoxAdv = new ComboBoxAdv() 
        { 
            Height = 30, 
            Width = 200, 
            HorizontalAlignment = HorizontalAlignment.Center, 
            VerticalAlignment = VerticalAlignment.Center 
        }; 
                  ComboBoxItemAdv item1 = new ComboBoxItemAdv() { Content = "Denmark" }; 
                  ComboBoxItemAdv item2 = new ComboBoxItemAdv() { Content = "New Zealand" }; 
                  ComboBoxItemAdv item3 = new ComboBoxItemAdv() { Content = "Canada" }; 
                  ComboBoxItemAdv item4 = new ComboBoxItemAdv() { Content = "Russia" }; 
                  ComboBoxItemAdv item5 = new ComboBoxItemAdv() { Content = "Japan" }; 
                  comboBoxAdv.Items.Add(item1); 
                  comboBoxAdv.Items.Add(item2); 
                  comboBoxAdv.Items.Add(item3); 
                  comboBoxAdv.Items.Add(item4); 
                  comboBoxAdv.Items.Add(item5); 
                  this.Content = comboBoxAdv; 
    } 
}