Improve CheckComboBox example

Elwig/Windows/TestWindow.xaml.cs

@@ -1,10 +1,18 @@
+using System.Collections.Generic;
 using System.Windows;
+using Xceed.Wpf.Toolkit.Primitives;
 
 namespace Elwig.Windows {
     public partial class TestWindow : Window {
         public TestWindow() {
             InitializeComponent();
-            _combo.ItemsSource = new string[] { "Klasse A", "Klasse B", "Klasse C", "Klasse D", "Klasse E", "Klasse F" };
+            MyComboBox.ItemsSource = new string[] { "Klasse A" , "Klasse B", "Klasse C", "Klasse D", "Klasse E", "Klasse F" };
+        }
+
+        private void OnItemSelectionChanged(object sender, ItemSelectionChangedEventArgs e) {
+            var selected = new List<string>();
+            foreach (var item in MyComboBox.SelectedItems) selected.Add((string)item);
+            MyText.Text = string.Join(", ", selected);
         }
     }
 }