How to add available SerialPort names to RibbonComboBox or RibbonGallery

With following code I add available serial port names to the RibbonGallery object:
xaml:

<ribbon:RibbonComboBox Name="cmbBoxComPortName" SelectionBoxWidth="40" Label="Port name:">
    <ribbon:RibbonGallery Name="galleryComPortName" SelectionChanged="galleryComPortName_SelectionChanged" />
</ribbon:RibbonComboBox>

code-behind c#:

galleryComPortName.ItemsSource = SerialPortAdapter.GetAvailablePortList();

SerialPortAdapter code:

class SerialPortAdapter
{
    public static List<string> GetAvailablePortList()
    {
        var portList = SerialPort.GetPortNames().ToList();
        portList.Sort();
        return portList;
    }
}

The problem is now, that the port names are present in the combobox but they are not selectable.

How can I select them and treat the event to set my port name?

Tags: C# (C# 4.0), Data binding, Serial port, Ribbon