How to get Cross selection of data

[#1]

By cross selection I mean the data that becomes selected when another set of data is being selected.

E.g. I have a sheet where I display a map, and another sheet where I have a list of customers. Each customer has an address. On the map I select some cities. The second sheet now displays only the customers who live in these cities.

I can get the list of the selected cities. Which method or a set of methods I should now call to get the list of the customers?

In the code:

using (var app = await location.AppAsync(appIdentifier))

{

    var fields = await app.GetAppFieldsAsync();

    var field = fields.First(x => x.Name == "City");

    var selectedCities = field.GetSelected(new List<NxPage> {new NxPage {Height = 30, Width = 1}});

    var selectedCustomers = ...?

}