如何在表单中链接功能？

Question

我尝试这样做 func Form1_Load 将显示城市列表。 我不知道如何将城市的 3 个函数（JerusalemData()、LondonData()、OttawaData()）链接到函数 FillCitiesData()； 问题是它不显示列表，而只显示街道而没有选择城市。另一个问题 - 在 HouseNum_ValueChanged 中，它不显示数字，您还可以输入字母而不仅仅是数字。 这是我的代码 - 如果有人能帮我找到问题，我会很高兴。

namespace PlanYourParty
{

    public partial class Form1 : Form
    {
        List <City> cities;
        List <string> streets;

        public Form1()
        {
            InitializeComponent();
            FillCitiesData();
        }

        public void FillCitiesData()
        {
            cities = new List<City>();
            cities.Add(new City() { Code = "123", Name = "Jerusalem" });
            cities.Add(new City() { Code = "456", Name = "London" });
            cities.Add(new City() { Code = "789", Name = "Ottawa" });
            JerusalemData();
            LondonData();
            OttawaData();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            FillCitiesData();
            cmbCity.DataSource = cities;
            cmbCity.DisplayMember = "Name";
            cmbCity.ValueMember = "Code";
            cmbCity.SelectedIndexChanged += cmbCity_SelectedIndexChanged;
        }


        public void JerusalemData()
        {
            streets = new List<string>();
            cmbStreet.Items.Clear();
            cmbStreet.Items.Add("Admond Peleg");
            cmbStreet.Items.Add("Pardes");
            cmbStreet.Items.Add("Nayman");
        }

        public void LondonData()
        {
            streets = new List<string>();
            cmbStreet.Items.Clear();
            cmbStreet.Items.Add("Oxford Street");
            cmbStreet.Items.Add("Piccadilly");
            cmbStreet.Items.Add("Highfield Ave");
        }

        public void OttawaData()
        {
            streets = new List<string>();
            cmbStreet.Items.Clear();
            cmbStreet.Items.Add("Riverside Drive");
            cmbStreet.Items.Add("Ontario Highway");
            cmbStreet.Items.Add("Moodie Drive");
        }

        private void cmbCity_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (sender != null && sender as City != null)
            {
                string code;
                code = (sender as City).Code;
                if (code == "123")
                {
                    JerusalemData();
                }
                else if (code == "456")
                {
                    LondonData();
                }
                else OttawaData();

            }

        }


        private void cmbStreet_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void domainUpDownHouseNumber_SelectedItemChanged(object sender, EventArgs e)
        {

        }

        private void Form1_Load_1(object sender, EventArgs e)
        {

        }

    }

Answer 1

首先，我建议您将数据模型与 UI 分开。在 City 类中提取定义城市和街道所需的一切。我在示例中包含了两种返回城市的方法，以及每个城市的街道。

不需要单独的方法来做同样的事情，但使用不同的数据。

City.cs

public class City
{
    public string Code { get; set; }
    public string Name { get; set; }
    public IList<string> Streets { get => GetStreets(this); }

    public static List<City> GetCities()
    {
        var cities = new List<City>();
        cities.Add(new City() { Code = "123", Name = "Jerusalem" });
        cities.Add(new City() { Code = "456", Name = "London" });
        cities.Add(new City() { Code = "789", Name = "Ottawa" });
        return cities;
    }

    public static List<string> GetStreets(City city)
    {
        var streets = new List<string>();
        if (city == null) return streets;
        switch (city.Code)
        {
            case "123":
                streets.Add("Admond Peleg");
                streets.Add("Pardes");
                streets.Add("Nayman");
                break;
            case "456":
                streets.Add("Oxford Street");
                streets.Add("Piccadilly");
                streets.Add("Highfield Ave");
                break;
            case "789":
                streets.Add("Riverside Drive");
                streets.Add("Ontario Highway");
                streets.Add("Moodie Drive");
                break;
            default:
                throw new ArgumentException("Unknown city code.");
        }
        return streets;
    }
}

然后编写 UI，使控件包含由 City.GetCities() 和 City.GetSreets() 方法指定的项目列表。

CurrentCity 和CurrentStreet 以及它们在CurrentCityIndex 和CurrentStreetIndex 组合框中的相应索引返回当前选定的城市和街道。

Form1.cs

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }


    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);

        cityComboBox.DataSource = City.GetCities();
        cityComboBox.DisplayMember = nameof(CurrentCity.Name);
        cityComboBox.ValueMember = nameof(CurrentCity.Code);
        cityComboBox.SelectedIndexChanged += CityComboBox_SelectedIndexChanged;
        cityComboBox.SelectedIndex = -1;    // remove default selection of 1st item.

        streetComboBox.DataSource = Array.Empty<string>();
        streetComboBox.SelectedIndexChanged += StreetComboBox_SelectedIndexChanged;
    }

    private void CityComboBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        // TODO: Things when a city is selected.
        streetComboBox.DataSource = CurrentCity?.Streets;
        streetComboBox.SelectedIndex = -1;  // remove default selection of 1st item.
        UpdateLabels();
    }

    private void StreetComboBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        // TODO: Things when a street is selected.
        UpdateLabels();
    }

    public void UpdateLabels()
    {
        cityInfo.Text = CurrentCityIndex >= 0 ? $"#{CurrentCity.Code} {CurrentCity.Name}" : "Please select a city.";
        streetInfo.Text = CurrentStreetIndex >= 0 ? CurrentStreet : "Please select a street.";
    }

    public List<City> AllCities { get => cityComboBox.DataSource as List<City>; }
    public List<string> AllStreets { get => streetComboBox.DataSource as List<string>; }

    public int CurrentCityIndex { get => cityComboBox.SelectedIndex; }
    public int CurrentStreetIndex { get => streetComboBox.SelectedIndex; }

    public City CurrentCity { get => cityComboBox.SelectedItem as City; }
    public string CurrentStreet { get => streetComboBox.SelectedItem as string; }
}

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