Winforms ComboBox DataBinding DisplayMember 到 SubObject 属性答案

【问题标题】：Winforms ComboBox DataBinding DisplayMember to SubObject PropertyWinforms ComboBox DataBinding DisplayMember 到 SubObject 属性
【发布时间】：2012-12-05 13:39:57
【问题描述】：

我搜索了 2 小时或更长时间，但找不到答案。所以我在这里试试：

我想知道如何（以及是否可以做到）我可以将模型列表数据绑定到 WinForms 组合框，并使用模型属性的属性（即在列表中）作为 DisplayMember 吗？在此处查看代码：

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; }
}

【问题讨论】：

您希望看到的 ValueMember 是什么？
作为 ValueMember，我使用 Home 本身。因为 ValueMember = "Home" 而不是 ValueMember = "Home.GeoLocationX" ，例如

标签： c# data-binding properties combobox

【解决方案1】：

只需在您的代码中添加一个方法（实际上是事件），它就可以工作了。

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; }
}

要创建此方法（事件），请在 [设计] 模式下转到您的表单，右键单击组合框 -> 属性。

在属性窗口的顶部，点击事件（闪电图标），

在下面的事件列表中（在 Property Changed 下）查找 Format 并在其中键入一些事件名称，例如：ComboBoxFormat，然后按 Enter。就是这样;)

【讨论】：

【解决方案2】：

Here 是一个类似的问题。在标记的答案中，您可以看到他们在ComboBox 上设置了Form 的BindingContext，这似乎对他们有用...

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

希望对您有所帮助...

【讨论】：

嗨，与绑定上下文无关（我认为）。我试过了，确实可以肯定，组合框无论如何都使用表单 bindingcontext（确实如此）：

【解决方案3】：

好的，我已经让 DisplayMember 工作了。您不能将“Home”用作 ValueMember 作为其对象，您必须指向其属性之一（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;

    }
}

【讨论】：

嗨 Derek，我也尝试过这个解决方案。它编译并......工作。但不是真的，因为我的 combobox1 只显示 1 个下拉字段：“芝麻街”。 comboBox1.Items.Count 也是 1。所以它真的不起作用。为什么？不知道...
抱歉，我再看看这个。
问题出在 HomeDataModel 上。您不能将它的三个属性包含在 UserDataModel 类中吗？我认为这将解决问题。
感谢您的努力，德里克！显然，我可以将属性添加到 UserDataModel，但这损害了我的问题的基础:) 而且我还有许多其他需要 SubProperty 的 DisplayMember 的组合框。如果我将所有这些类合二为一，您会称其为“优秀的软件设计”吗？ :)
我对您应用程序的其余部分一无所知。 @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遍。

【解决方案4】：

澄清一下：默认情况下，ComboBox 始终使用托管表单 BindingContext。我用该代码对其进行了测试：

            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");
            }
        }

消息框已显示。

【讨论】：