Winforms ComboBox数据绑定DisplayMember到子对象属性

Question

我搜寻了2个小时还是找不到答案，所以我在这里尝试求助:

我想知道怎样（如果可能）可以将一个模型列表数据绑定到WinForms下拉框，并使用列表中某个模型的属性中嵌套的属性作为显示成员(DisplayMember)? 代码如下：

public partial class Form1 : Form
{
    private List<UserDataModel> userData = new List<UserDataModel>();

    public Form1()
    {
        InitializeComponent();

        MyInit();
    }

    public void MyInit()
    {
        var userDataModel1 = new UserDataModel();
        userDataModel1.Name = "Mike";
        userDataModel1.Phone = "555-666";
        userDataModel1.Home = new HomeDataModel();
        userDataModel1.Home.StreetName = "MikeStreet";
        userDataModel1.Home.GeoLocationX = 111;
        userDataModel1.Home.GeoLocationY = 222;

        var userDataModel2 = new UserDataModel();
        userDataModel2.Name = "Jonathan";
        userDataModel2.Phone = "777-888";
        userDataModel2.Home = new HomeDataModel();
        userDataModel2.Home.StreetName = "JonathanStreet";
        userDataModel2.Home.GeoLocationX = 333;
        userDataModel2.Home.GeoLocationY = 444;

        userData.Add(userDataModel1);
        userData.Add(userDataModel2);

        // This works as usually:
        /*
        comboBox1.DisplayMember = "Name";
        comboBox1.ValueMember = "Home";
        comboBox1.DataSource = userData;
        */

        // But this works not (either with comboBox1.DataBindings.Add() nor with BindingSource):
        comboBox1.DisplayMember = "Home.StreetName";
        comboBox1.ValueMember = "Home";
        comboBox1.DataSource = userData;

        // To drive me crazy, THAT shit works:
        textBox1.DataBindings.Add("Text", userData, "Home.StreetName");

        /*
        So how can i use a String-Property of a SubObject as ComboBox-DisplayMember ???

        BTW: To rebuild the sample, you only need a normal Forms Application and
        then drop a ComboBox and a TextBox on it. Copy that code here, and run it.
        */
    }
}

internal sealed class UserDataModel
{
    public string Name { get; set; }
    public string Phone { get; set; }
    public HomeDataModel Home { get; set; }
}

internal sealed class HomeDataModel
{
    public string StreetName { get; set; }
    public int GeoLocationX { get; set; }
    public int GeoLocationY { get; set; }
}

- MBODM

---

你想将什么作为ValueMember呈现？ - Hamlet Hakobyan

作为 ValueMember，我使用 Home 本身。这总是很好的工作，因为 ValueMember =“Home”，而不是 ValueMember =“Home.GeoLocationX”等。 - MBODM

Answer 1

你的代码中新增了一个方法（其实是事件），而且它已经能够正常工作了。

public partial class Form1 : Form
{
    private List<UserDataModel> userData = new List<UserDataModel>();
    public Form1()
    {
        InitializeComponent();

        MyInit();
    }

    public void MyInit()
    {
        var userDataModel1 = new UserDataModel();
        userDataModel1.Name = "Mike";
        userDataModel1.Phone = "555-666";
        userDataModel1.Home = new HomeDataModel();
        userDataModel1.Home.StreetName = "MikeStreet";
        userDataModel1.Home.GeoLocationX = 111;
        userDataModel1.Home.GeoLocationY = 222;

        var userDataModel2 = new UserDataModel();
        userDataModel2.Name = "Jonathan";
        userDataModel2.Phone = "777-888";
        userDataModel2.Home = new HomeDataModel();
        userDataModel2.Home.StreetName = "JonathanStreet";
        userDataModel2.Home.GeoLocationX = 333;
        userDataModel2.Home.GeoLocationY = 444;

        userData.Add(userDataModel1);
        userData.Add(userDataModel2);

        // This works as usually:
        /*
        comboBox1.DisplayMember = "Name";
        comboBox1.ValueMember = "Home";
        comboBox1.DataSource = userData;
        */

        // But this works not (either with comboBox1.DataBindings.Add() nor with BindingSource):
        comboBox1.DisplayMember = "Home.StreetName";
        comboBox1.ValueMember = "Home";
        comboBox1.DataSource = userData;

        // To drive me crazy, THAT shit works:
        textBox1.DataBindings.Add("Text", userData, "Home.StreetName");

        /*
        So how can i use a String-Property of a SubObject as ComboBox-DisplayMember ???

        BTW: To rebuild the sample, you only need a normal Forms Application and
        then drop a ComboBox and a TextBox on it. Copy that code here, and run it.
        */
    }

    // To add this method - follow to my instructions below
    private void ComboBoxFormat(object sender, ListControlConvertEventArgs e)
    {
        e.Value = ((UserDataModel)e.ListItem).Home.StreetName;
    }
}

internal sealed class UserDataModel
{
    public string Name { get; set; }
    public string Phone { get; set; }
    public HomeDataModel Home { get; set; }
}

internal sealed class HomeDataModel
{
    public string StreetName { get; set; }
    public int GeoLocationX { get; set; }
    public int GeoLocationY { get; set; }
}

要创建这个方法（事件），请进入表单的[设计]模式，在ComboBox上单击右键 ->属性。

在属性窗口的顶部，单击事件（闪电图标）。

在下面的事件列表中（在属性更改下面），查找格式，并在其中输入一些事件名称，比如：ComboBoxFormat ，然后按Enter键。 就这样;)

- Eliran Kuta

Answer 2

好的，我已经让 DisplayMember 正常工作了。你不能使用 "Home" 作为 ValueMember，因为它是一个对象，你必须指向它的一个属性（StreetName、GeoLocationX、GeoLocationY）。

public partial class Form1 : Form
    {

        private List<UserDataModel> userData = new List<UserDataModel>();

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

        public void MyInit()
    {
        var mymodel = new UserDataModel("Derek", "999-999", new HomeDataModel("Sesame Street", 111, 222));

        var mymodel1 = new UserDataModel("John", "999-999", new HomeDataModel("Tin Can Alley", 333, 444));

        userData.Add(mymodel);
        userData.Add(mymodel1);

        BindingSource bs = new BindingSource();
        bs.DataSource = userData;

        comboBox1.DataSource = bs;
        comboBox1.DisplayMember = "Home.StreetName";

    }
}

internal sealed class UserDataModel
{
    public string Name { get; set; }
    public string Phone { get; set; }
    public HomeDataModel Home { get; set; }

    public UserDataModel()
    {

    }

    public UserDataModel(string name, string phone, HomeDataModel home)
    {
        this.Name = name;
        this.Phone = phone;
        this.Home = home;
    }
}

internal sealed class HomeDataModel
{
    public string StreetName { get; set; }
    public int GeoLocationX { get; set; }
    public int GeoLocationY { get; set; }

    public HomeDataModel()
    {

    }

    public HomeDataModel(string streetname, int x, int y)
    {
        this.StreetName = streetname;
        this.GeoLocationX = x;
        this.GeoLocationY = y;

    }
}

- Derek

---

嗨 Derek，我也尝试了那个解决方案。它编译并且...运行了。但实际上并没有真正起作用，因为我的comboBox1只显示了一个下拉字段：“芝麻街”。comboBox1.Items.Count也是1。所以它并没有真正地起作用。为什么？我不知道... - MBODM

抱歉，我会再次查看这个。 - Derek

问题出在HomeDataModel上。您能否不将其三个属性包含在UserDataModel类中？我认为这样可以解决问题。 - Derek

感谢您的努力，Derek！显然，我可以将属性添加到UserDataModel中，但这会伤害我的问题的根本。我还有许多其他需要SubProperty的ComboBox。如果我将所有这些类放入一个类中，您会称其为“良好的软件设计”吗？ :) - MBODM

我对你的整个应用程序没有概念。@马塞尔。这是一个有趣的问题。我会在今天的某个时候再看一下它。 - Derek

Answer 3

澄清一下：ComboBox 默认情况下始终使用宿主窗体的 BindingContext。我用以下代码进行了测试：

            var bc = comboBox1.BindingContext;
        if (bc == this.BindingContext)
        {
            if (bc.Equals(this.BindingContext))
            {
                MessageBox.Show("combobox always use same binding context as his hosting form");
            }
        }

并且消息框已显示。

- MBODM

Answer 4

这里有一个类似的问题。在标记的答案中，您可以看到他们将Form的BindingContext设置在ComboBox上，这似乎对他们有效...

//...
comboBox1.BindingContext = this.BindingContext;

希望这有所帮助...

- tweakch

---

嗨，我认为这与绑定上下文无关。我尝试了一下，确保ComboBox仍然使用表单的绑定上下文（它确实如此）：<请参见下面我的答案中的代码（因为这里没有代码格式）> - MBODM