c# - WPF 绑定(bind)因 INotifyPropertyChanged.PropertyChanged 的​​自定义添加和删除访问器而失败

Question

我有一个场景导致 WPF 数据绑定(bind)和 INotifyPropertyChanged 出现奇怪的行为。我想要数据绑定(bind)源的私有(private)成员来处理 INotifyPropertyChanged.PropertyChanged 事件。

这是源代码:

XAML

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="TestApplication.MainWindow"
    DataContext="{Binding RelativeSource={RelativeSource Self}}"
    Height="100" Width="100">
    <StackPanel>
        <CheckBox IsChecked="{Binding Path=CheckboxIsChecked}" Content="A" />
        <CheckBox IsChecked="{Binding Path=CheckboxIsChecked}" Content="B" />
    </StackPanel>
</Window>

正常实现工作

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public bool CheckboxIsChecked
    {
        get { return this.mCheckboxIsChecked; }
        set
        {
            this.mCheckboxIsChecked = value;
            PropertyChangedEventHandler handler = this.PropertyChanged;
            if (handler != null)
                handler(this, new PropertyChangedEventArgs("CheckboxIsChecked"));
        }
    }

    private bool mCheckboxIsChecked = false;

    public MainWindow() { InitializeComponent(); }
}

期望的实现不工作

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged
    {
        add { lock (this.mHandler) { this.mHandler.PropertyChanged += value; } }
        remove { lock (this.mHandler) { this.mHandler.PropertyChanged -= value; } }
    }

    public bool CheckboxIsChecked
    {
        get { return this.mHandler.CheckboxIsChecked; }
        set { this.mHandler.CheckboxIsChecked = value; }
    }

    private HandlesPropertyChangeEvents mHandler = new HandlesPropertyChangeEvents();

    public MainWindow() { InitializeComponent(); }

    public class HandlesPropertyChangeEvents : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public bool CheckboxIsChecked
        {
            get { return this.mCheckboxIsChecked; }
            set
            {
                this.mCheckboxIsChecked = value;
                PropertyChangedEventHandler handler = this.PropertyChanged;
                if (handler != null)
                    handler(this, new PropertyChangedEventArgs("CheckboxIsChecked"));
            }
        }

        private bool mCheckboxIsChecked = false;
    }
}

Answer 1

这只是一个猜测，但我认为这可能是因为传递给事件处理程序的 sender 参数是 HandlesPropertyChangeEvents 的实例，而绑定(bind)需要一个实例主窗口。

尝试更改您的代码，以便发件人是 MainWindow 实例:

private PropertyChangedEventHandler _propertyChanged;
public event PropertyChangedEventHandler PropertyChanged
{
    add { lock (this.mHandler) { this._propertyChanged += value; } }
    remove { lock (this.mHandler) { this._propertyChanged -= value; } }
}


...

public MainWindow()
{
    InitializeComponent();
    mHandler.PropertyChanged += mHandler_PropertyChanged;
}

private void mHandler_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    var handler = _propertyChanged;
    if (handler != null)
        _propertyChanged(this, e);
}