c#绑定到嵌套对象上的字段

Question

我似乎无法找到一个简单,具体的解释,说明如何使用数据绑定将WinForms应用程序中的控件绑定到嵌套对象.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,第一个用于Name,第二个用于Inner.SomeValue.我可以很容易地绑定对Name工作,但Inner.SomeValue是片状的.如果我填充对象然后设置绑定,它会在文本框中显示Inner.SomeValue但我无法编辑它.如果我在没有初始化Inner的情况下从一个新对象开始,我似乎无法将数据保留在Inner.SomeValue中.

我已经检查了整个MSDN,遍布StackOverflow,以及使用不同关键字的数十个搜索.每个人都想谈论绑定到数据库或DataGrids,大多数示例都是用XAML编写的.

更新:我已经尝试过Marc的全部测试工具并取得了部分成功.如果我点击"全部改变!" 按钮,我似乎能够回写内部对象.但是,从MyObject.Inner null开始,它不知道如何创建内部对象.我想现在,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,我情不自禁地觉得我错过了什么:)

Answer 1

嗯 - 一个很好的问题；我已经对对象进行了大量数据绑定，我发誓你所做的应该有效；但确实很不愿意注意到内在对象的变化。我设法通过以下方式使其工作：

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

不理想，但它有效。顺便提一句; 您可能会发现以下实用方法很有用：

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));
    }
}

然后你可以有：

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;
}

并且在讨价还价中，它修复了空异常（竞争条件）的（微薄）机会。

完整的测试装置，以消除扭结（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);
        }
    }

}