Add CheckComboBox

Elwig/Windows/TestWindow.xaml

@@ -0,0 +1,16 @@
+<Window x:Class="Elwig.Windows.TestWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:local="clr-namespace:Elwig.Windows"
+        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
+        Title="Test Fenster - Elwig" MinHeight="400" MinWidth="325" Height="450" Width="800" ResizeMode="CanResize">
+    <Grid>
+        <xctk:CheckComboBox x:Name="_combo" Width="200"
+                            HorizontalAlignment="Center"
+                            VerticalAlignment="Center"
+                            SelectedValue="{Binding SelectedValue}"
+                            SelectedItemsOverride="{Binding SelectedItems}"/>
+    </Grid>
+</Window>