wpf ef zipcode combobox question

Using wpf and ef 6.  I have a lookup table for zipcodes.  This table has zip, city, and state.  On a wpf window, there is a combobox for zip, a textbox for city, and a textbox for state.  How do I automatically supply the city and state based on the zipcode selected?

Code to bind combo:

        Dim zipCodeList = From z In _context.tlkpZipCodes _
                          Order By z.ZipCode
        Dim zipCodeSource = CType(Me.FindResource("ZipCodeLookup"), CollectionViewSource)
        zipCodeSource.Source = zipCodeList.ToList

Xaml:

<Window.Resources><CollectionViewSource x:Key="ZipCodeLookup" /></Window.Resources><Grid DataContext="{StaticResource MyResource}">
         ...snip...<Label Content="Zip:" HorizontalAlignment="Left" Margin="103,184,0,0" VerticalAlignment="Top"/><ComboBox Name="cboZip" HorizontalAlignment="Left" Margin="137,184,0,0" VerticalAlignment="Top" Width="120" 
                  DisplayMemberPath="ZipCode" 
                  ItemsSource="{Binding Source={StaticResource ZipCodeLookup}}" /><Label Content="City:" HorizontalAlignment="Left" Margin="99,210,0,0" VerticalAlignment="Top"/><TextBox Name="txtCity" HorizontalAlignment="Left" Height="23" Margin="137,210,0,0" TextWrapping="Wrap" 
                                  VerticalAlignment="Top" Width="120"/><Label Content="State:" HorizontalAlignment="Left" Margin="93,238,0,0" VerticalAlignment="Top"/><TextBox Name="txtState" HorizontalAlignment="Left" Height="23" Margin="137,238,0,0" TextWrapping="Wrap" 
                 VerticalAlignment="Top" Width="120"/>

For example, if the zipcode lookup table contains this row:

     10028, "New York", "NY"

and the user chooses 10028 from the combo, "New York" will appear in the city textbox and "NY" will appear in the state textbox.

Thanks.