C＃绑定到嵌套对象上的字段

Question

我似乎找不到使用数据绑定在Winforms应用程序中绑定控件中的控件与嵌套对象的简单，具体的解释。例如：

class MyObject : INotifyPropertyChanged
{
    private string _Name;
    public string Name 
    { 
        get { return _Name; } 
        set 
        { 
            _Name = value; 
            OnPropertyChanged("Name"); 
        }    
    }

    private MyInner _Inner;
    public MyInner Inner 
    { 
       get { return _Inner; } 
       set 
       { 
           _Inner = value; 
           OnPropertyChanged("Inner"); 
       } 
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

class MyInner : INotifyPropertyChanged
{
    private string _SomeValue;
    public string SomeValue 
    {
        get { return _SomeValue; } 
        set 
        { 
            _SomeValue = value; 
            OnPropertyChanged("SomeValue"); 
        } 
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

现在，想象一个只有两个文本框的表单，第一个是姓名，第二个是innit.somebalue。我很容易就可以与名称作用，但是内在价值是片状的。如果我填充对象然后设置绑定，则在文本框中显示innear.somebebalue，但我无法编辑它。如果我从新鲜的对象开始而不初始化内部对象，那么我似乎无法将数据粘贴在inner.somebalue中。

我已经检查了整个MSDN，遍布Stackoverflow，并使用了数十个具有不同关键字的搜索。每个人都想谈论与数据库或数据杂志的绑定，并且大多数示例都是用XAML编写的。

更新：我尝试了MARC的完整测试安全带，并取得了部分成功。如果我打“全部变化！”按钮，我似乎能够回到内部对象。但是，从myObject.inner null开始，它不知道如何创建内部对象。我认为目前，我可以通过确保我的内部引用始终设置为有效对象来解决它。不过，我不禁感到自己缺少一些东西:)

Answer 1

嗯 - 一个很好的问题；我已经对对象做了很多数据结合，我将 发誓 你正在做的应该有效；但是确实，注意到内部对象的变化是非常不愿意的。我设法通过：

var outer = new BindingSource { DataSource = myObject };
var inner = new BindingSource(outer, "Inner");
txtName.DataBindings.Add("Text", outer, "Name");
txtSomeValue.DataBindings.Add("Text", inner, "SomeValue");

不是理想的，但它起作用。顺便提一句;您可能会发现以下实用程序方法有用：

public static class EventUtils {
    public static void SafeInvoke(this EventHandler handler, object sender) {
        if(handler != null) handler(sender, EventArgs.Empty);
    }
    public static void SafeInvoke(this PropertyChangedEventHandler handler,
               object sender, string propertyName) {
        if(handler != null) handler(sender,
               new PropertyChangedEventArgs(propertyName));
    }
}

然后，您可以：

class MyObject : INotifyPropertyChanged
{
    private string _Name;
    public string Name { get { return _Name; } set {
        _Name = value; PropertyChanged.SafeInvoke(this,"Name"); } }
    private MyInner _Inner;
    public MyInner Inner { get { return _Inner; } set {
        _Inner = value; PropertyChanged.SafeInvoke(this,"Inner"); } }
    public event PropertyChangedEventHandler PropertyChanged;
}

class MyInner : INotifyPropertyChanged
{
    private string _SomeValue;
    public string SomeValue { get { return _SomeValue; } set {
        _SomeValue = value; PropertyChanged.SafeInvoke(this, "SomeValue"); } }
    public event PropertyChangedEventHandler PropertyChanged;
}

在讨价还价中，它解决了无效的（种族条件）的（纤细）机会。

---

完整的测试钻机，以熨烫扭结（来自评论）：

using System;
using System.ComponentModel;
using System.Windows.Forms;
public static class EventUtils {
    public static void SafeInvoke(this PropertyChangedEventHandler handler, object sender, string propertyName) {
        if(handler != null) handler(sender, new PropertyChangedEventArgs(propertyName));
    }
}
class MyObject : INotifyPropertyChanged
{
    private string _Name;
    public string Name { get { return _Name; } set { _Name = value; PropertyChanged.SafeInvoke(this,"Name"); } }
    private MyInner _Inner;
    public MyInner Inner { get { return _Inner; } set { _Inner = value; PropertyChanged.SafeInvoke(this,"Inner"); } }
    public event PropertyChangedEventHandler PropertyChanged;
}

class MyInner : INotifyPropertyChanged
{
    private string _SomeValue;
    public string SomeValue { get { return _SomeValue; } set { _SomeValue = value; PropertyChanged.SafeInvoke(this, "SomeValue"); } }
    public event PropertyChangedEventHandler PropertyChanged;
}
static class Program
{
    [STAThread]
    public static void Main() {
        var myObject = new MyObject();
        myObject.Name = "old name";
        // optionally start with a default
        //myObject.Inner = new MyInner();
        //myObject.Inner.SomeValue = "old inner value";

        Application.EnableVisualStyles();
        using (Form form = new Form())
        using (TextBox txtName = new TextBox())
        using (TextBox txtSomeValue = new TextBox())
        using (Button btnInit = new Button())
        {
            var outer = new BindingSource { DataSource = myObject };
            var inner = new BindingSource(outer, "Inner");
            txtName.DataBindings.Add("Text", outer, "Name");
            txtSomeValue.DataBindings.Add("Text", inner, "SomeValue");
            btnInit.Text = "all change!";
            btnInit.Click += delegate
            {
                myObject.Name = "new name";
                var newInner = new MyInner();
                newInner.SomeValue = "new inner value";
                myObject.Inner = newInner;
            };
            txtName.Dock = txtSomeValue.Dock = btnInit.Dock = DockStyle.Top;
            form.Controls.AddRange(new Control[] { btnInit, txtSomeValue, txtName });
            Application.Run(form);
        }
    }

}