c# - 检测数据上下文的属性更改

Question

Clemen 在这里的精彩回答还有一个问题:DataContext values in view code behind .如果使用这种方法，此时是否可以检测到 VM 上的属性更改？这些是通过 INotifyPropertyChanged 正确实现的。

var viewModel = DataContext as MyViewModel;
//How would one detect a property change on viewModel?
//Tried viewModel.PropertyChange which doesn't fire.

Answer 1

我认为您一定做错了您在帖子中没有提及的事情。以下代码按预期工作，并将 MyTestPropertyName 打印到控制台窗口。

public partial class MainWindow : Window
{

    public MainWindow()
    {
        DataContext = new MyViewModel();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        MyViewModel viewModel = DataContext as MyViewModel;
        viewModel.PropertyChanged += MyPropertyChangedEventHandler;
        viewModel.NotifyPropertyChanged();
    }

    private void MyPropertyChangedEventHandler(object sender, PropertyChangedEventArgs e)
    {
        Console.WriteLine(e.PropertyName);
    }

}

public class MyViewModel : INotifyPropertyChanged
{
    public void NotifyPropertyChanged()
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs("MyTestPropertyName"));
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion
}

应该注意的是，这是一个糟糕的设计，仅作为概念证明而设计，您确实可以在代码隐藏中订阅 ViewModel 上的事件。