Datagrid组合框数据绑定更新MVVM

Question

我在理解如何使用嵌入数据网格中的组合框时遇到了问题。例如，我有一个绑定到GridModel类的数据网格：

public partial class MainWindow : Window
{
    public GridModel gridModel { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        gridModel = new GridModel();
        dgCustomers.DataContext = gridModel;
    }
}

GridModel类是：

public class GridModel : ViewModelBase
{
    public ObservableCollection<Record> customers { get; set; }
    public List<Country> countries { get; set; }
    public GridModel()
    {
        customers = new ObservableCollection<Record>();
        customers.Add(new Record { name = "Alan", phone = "123" });
        customers.Add(new Record { name = "Bert", phone = "234" });
        countries = new List<Country> { new Country { id = 1, name = "England", code = 44 }, new Country { id = 2, name = "Germany", code = 49 } };
    }
}

XAML是：

<Window x:Class="Customer.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
<Grid>
    <DataGrid x:Name="dgCustomers" AutoGenerateColumns="False" ItemsSource="{Binding customers}">
        <DataGrid.Resources>
            <DataTemplate x:Key="dgCombobox">
                <ComboBox   x:Name="cmbCountry"
                            ItemsSource="{Binding countries}"
                            DisplayMemberPath="{Binding name}"
                            SelectedValue="{Binding customers.countryCode, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                            SelectedValuePath="{Binding code}">
                </ComboBox>
            </DataTemplate>
        </DataGrid.Resources>
        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding name}"/>
            <DataGridTemplateColumn Header="Country" CellTemplate="{StaticResource dgCombobox}" />
            <DataGridTextColumn Header="Phone" Binding="{Binding phone}" ></DataGridTextColumn>
        </DataGrid.Columns>
    </DataGrid>

</Grid>

第二列中的组合框应该从模型的countries属性填充，这是类Country的列表：

public class Country : ViewModelBase
{
    private string _name;
    public string name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged("name");
        }
    }

    private int _id;
    public int id
    {
        get { return _id; }
        set
        {
            _id = value;
            OnPropertyChanged("id");
        }
    }

    private int _code;
    public int code
    {
        get { return _code; }
        set
        {
            _code = value;
            OnPropertyChanged("code");
        }
    }
}

组合框应显示国家/地区名称。数据网格是从类记录的客户ObservableCollection中填充的：

public class Record : ViewModelBase
{
    private string _name;
    public string name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged("name");
        }
    }

    private string _phone;
    public string phone
    {
        get { return _phone; }
        set
        {
            _phone = value;
            OnPropertyChanged("phone");
        }
    }

    private int _countryCode;
    public int countryCode
    {
        get { return _countryCode; }
        set
        {
            _countryCode = value;
            OnPropertyChanged("countryCode");
        }
    }
}

为了完整起见，这里是ViewModelBase类：

public class ViewModelBase : INotifyPropertyChanged
{
    public ViewModelBase()
    {

    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

我想要的是用户能够从每行的组合框中为客户选择一个国家/地区，然后该行的记录将其countryCode属性设置为所选国家/地区的代码属性。我使用了datagridtemplatecolumn，以便在网格上显示组合框。任何帮助表示赞赏，我已经对这个问题感到震惊了一个多月，我开始感到非常愚蠢。