DataContext dc = new DataContext();
ObservableCollection<Customer> customers = new ObservableCollection<Customer>();
ObservableCollection<Country> countries = new ObservableCollection<Country>();
var queryAllCustomers = dc.Customers;
var queryAllCountries = dc.Countries;
foreach (Customer customer in queryAllCustomers)
{
    customers.Add(customer);
}
foreach (Country country in queryAllCountry)
{
    countries.Add(country);
}