In my opinion, you have to set the DataTemplate for that Combobox to display the data.
But you have to set the DataContext of the Combobox to your class.
Do this in you code-behind:
myComboBox.DataContext=Classes;
It goes like this:
<combobox name="myCombobox" itemssource="{Binding}">
<combobox.itemtemplate>
<datatemplate>
<textblock text="{Binding Path=Yourproperty}" />
</datatemplate>
</combobox.itemtemplate>
</combobox>
where "Yourproperty" is the property of that class whose value is to be displayed.
or you can also set the DisplayMemerBinding directly to the ComboBox :
<combobox name="Acombo" itemssource="{Binding}" displaymemberbinding="{Binding Path=Yourproperty}" />