Populating the WPF ComboBox with System Font Families is so easy and can be done in XAML without code behind.

<ComboBox x:Name="fonts" 
Width="200" 
ItemsSource="{Binding Source={x:Static Member=Fonts.SystemFontFamilies}}" />
Also to show each Font Item with its own corresponding Font Family, just modifying the Item template will make the magic.
<ComboBox.ItemTemplate>
   <DataTemplate>
        <TextBlock Text="{Binding}" FontFamily="{Binding}"/>
    </DataTemplate>
</ComboBox.ItemTemplate>


Happy coding…