如何在DataGridView控件中实现级联ComboBox？

我需要ComboBoxes在几DataGridView秒钟内实现级联。作为概念验证，我整理了以下代码。3列（“客户”，“国家/地区”，“城市”）在选择“国家/地区”时，应填充城市，但不起作用。

有没有更好的方法来实现这一目标并解决我做错的事情？

public partial class Form1 : Form
{
    private List<Customer> customers;
    private List<Country> countries;
    private List<City> cities;
    private ComboBox cboCountry;
    private ComboBox cboCity;
    public Form1()
    {
        InitializeComponent();
        countries = GetCountries();
        customers = GetCustomers();

        SetupDataGridView();

    }

    private List<Customer> GetCustomers()
    {
        var customerList = new List<Customer>
                          {
                              new Customer {Id=1,Name = "Jo",Surname = "Smith"},
                              new Customer {Id=2,Name = "Mary",Surname = "Glog"},
                              new Customer {Id=3,Name = "Mark",Surname = "Bloggs"}
                          };

        return customerList;
    }

    private List<Country> GetCountries()
    {
        var countryList = new List<Country>
                          {
                              new Country {Id=1,Name = "England"},
                              new Country {Id=2,Name = "Spain"},
                              new Country {Id=3,Name = "Germany"}
                          };

        return countryList;
    }
    private List<City> GetCities(string countryName)
    {
        var cityList = new List<City>();
        if (countryName == "England") cityList.Add(new City { Id = 1, Name = "London" });
        if (countryName == "Spain") cityList.Add(new City { Id = 2, Name = "Madrid" });
        if (countryName == "Germany") cityList.Add(new City { Id = 3, Name = "Berlin" });

        return cityList;
    }

    private void SetupDataGridView()
    {
        dataGridView1.CellLeave += dataGridView1_CellLeave;
        dataGridView1.EditingControlShowing += dataGridView1_EditingControlShowing;

        DataGridViewTextBoxColumn colCustomer = new DataGridViewTextBoxColumn();
        colCustomer.Name = "colCustomer";
        colCustomer.HeaderText = "CustomerName";

        DataGridViewComboBoxColumn colCountry = new DataGridViewComboBoxColumn();
        colCountry.Name = "colCountry";
        colCountry.HeaderText = "Country";


        DataGridViewComboBoxColumn colCity = new DataGridViewComboBoxColumn();
        colCity.Name = "colCity";
        colCity.HeaderText = "City";


        dataGridView1.Columns.Add(colCustomer);
        dataGridView1.Columns.Add(colCountry);
        dataGridView1.Columns.Add(colCity);


        //Databind gridview columns
        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCountry"]).DisplayMember = "Name";
        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCountry"]).ValueMember = "Id";
        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCountry"]).DataSource = countries;

        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCity"]).DisplayMember = "Name";
        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCity"]).ValueMember = "Id";
        ((DataGridViewComboBoxColumn)dataGridView1.Columns["colCity"]).DataSource = cities;

        foreach (Customer cust in customers)
        {
            dataGridView1.Rows.Add(cust.Name + " " + cust.Surname);
        }
    }

    private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
        //register a event to filter displaying value of items column.
        if (dataGridView1.CurrentRow != null && dataGridView1.CurrentCell.ColumnIndex == 2)
        {
            cboCity = e.Control as ComboBox;
            if (cboCity != null)
            {
                cboCity.DropDown += cboCity_DropDown;
            }
        }

        //Register SelectedValueChanged event and reset item comboBox to default if category changes
        if (dataGridView1.CurrentRow != null && dataGridView1.CurrentCell.ColumnIndex == 1)
        {
            cboCountry = e.Control as ComboBox;
            if (cboCountry != null)
            {
                cboCountry.SelectedValueChanged += cboCountry_SelectedValueChanged;
            }
        }
    }

    void cboCountry_SelectedValueChanged(object sender, EventArgs e)
    {
        //If category value changed then reset item to default.
        dataGridView1.CurrentRow.Cells[2].Value = 0;
    }

    void cboCity_DropDown(object sender, EventArgs e)
    {
        string countryName = dataGridView1.CurrentRow.Cells[1].Value.ToString();
        List<City> cities = new List<City>();

        cities = GetCities(countryName);
        cboCity.DataSource = cities;
        cboCity.DisplayMember = "Name";
        cboCity.ValueMember = "Id";


    }

    private void dataGridView1_CellLeave(object sender, DataGridViewCellEventArgs e)
    {
        if (cboCity != null) cboCity.DropDown -= cboCity_DropDown;
        if (cboCountry != null)
        {
            cboCountry.SelectedValueChanged -= cboCountry_SelectedValueChanged;
        }
    }
}

public class Country
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class City
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
}

}