var d = new Dictionary<string, List<string>>();
var str = "la,la,la";
d.Add("Lalala", str.Split(',').ToList());
str = "bla,bla,bla";
d.Add("Blablabla", str.Split(',').ToList());
str = "a,a,a";
d.Add("Aaa", str.Split(',').ToList());
Resources["Ranges"] = d;

<ComboBox Margin="2,0" ItemsSource="{DynamicResource Ranges}"/>

        <ComboBox ...>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Path=Key}"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ComboBox>