属性没有得到 NotifyPropertyChanged

Question

我有一个包含 3 个文件的小应用程序。第一个文件是Authentication，它继承自第二个文件ObservableObject。此文件继承INotifyPropertyChanged。

class Authentication : ObservableObject
{
    public void Start()
    {
        Auth = Visibility.Visible;
        Tab = Visibility.Collapsed;
    }

    public void SetView()
    {
        Auth = Visibility.Collapsed;
        Tab = Visibility.Visible;
    }

    public Visibility Auth { get; set; }
    public Visibility Tab { get; set; }
    public Visibility Admin { get; set; }
    public Visibility Planner { get; set; }
    public Visibility WorkPrep { get; set; }
    public Visibility Leader { get; set; }
    public Visibility PreSet { get; set; }
    public Visibility Measure { get; set; }
    public Visibility Worker { get; set; }
}

我的第三个文件是我的 View 的 ViewModel。

class MainWindowViewModel : ObservableObject
{
    private Authentication auth = new Authentication();

    public MainWindowViewModel()
    {
        LogIn = new RelayCommand(() => auth.SetView(), () => (string.IsNullOrEmpty(Username) || string.IsNullOrEmpty(Password)) ? false : true);
        auth.Start();
    }

    public ICommand LogIn { get; set; }
    public Visibility Auth
    {
        get
        {
            return auth.Auth;
        }
        set
        {
            auth.Auth = value;
            NotifyPropertyChanged();
        }
    }
    public Visibility Tab
    {
        get
        {
            return auth.Tab;
        }
        set
        {
            auth.Tab = value;
            NotifyPropertyChanged();
        }
    }
}

现在，当我启动应用程序时，auth.Start(); 被正确执行并设置了正确的Visibility。当我按下绑定到Command LogIn 的Button 时，auth.SetView(); 被执行但Visibilities 没有更新。

我的结论是，当我加载应用程序时，Visibilities 设置正确，但一旦加载，它就不会从 Authentication 类更新为 MainWindowViewModel 类。

---

编辑：这是对这个问题可能很重要的 ObservableObject 类。

public class ObservableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Answer 1

您通过 Authentication 类更新 Auth 的可见性，这不会导致 NotifyProperty 事件被触发。我在 Authentication 类中添加了对 NotifyPropertyChanged 方法的调用：

class Authentication : ObservableObject
{
    public void Start()
    {
        Auth = Visibility.Visible;
        Tab = Visibility.Collapsed;
    }

    public void SetView()
    {
        Auth = Visibility.Collapsed;
        Tab = Visibility.Visible;
    }

    private Visibility auth;
    public Visibility Auth
    {
        get
        {
            return auth;
        }
        set
        {
            auth= value;
            NotifyPropertyChanged();
        }
    }

    private Visibility tab;
    public Visibility Tab
    {
        get
        {
            return tab;
        }
        set
        {
            tab = value;
            NotifyPropertyChanged();
        }
    }
    // etc
}

现在，我们只是在 MainWindowViewModel 中回显每个 NotifyProperty 事件（在这种情况下应该足够了）。

class MainWindowViewModel : ObservableObject
{
    private Authentication auth = new Authentication();

    public MainWindowViewModel()
    {
        LogIn = new RelayCommand(() => auth.SetView(), () => (string.IsNullOrEmpty(Username) || string.IsNullOrEmpty(Password)) ? false : true);

        // Echo the PropertyChanged events from our auth class
        auth.PropertyChanged += (sender, e) =>
        {
            if (PropertyChanged != null)
                PropertyChanged(sender, e);
        }

        auth.Start();
    }

    public ICommand LogIn { get; set; }
    public Visibility Auth
    {
        get
        {
            return auth.Auth;
        }
        set
        {
            auth.Auth = value;
            NotifyPropertyChanged();
        }
    }
    public Visibility Tab
    {
        get
        {
            return auth.Tab;
        }
        set
        {
            auth.Tab = value;
            NotifyPropertyChanged();
        }
    }
}