我需要在代码隐藏中调用 INotifyPropertyChanged() 吗？

Question

在我的程序中，当我的另一个 contentPresenter 获得焦点时，我想禁用 contentPresenter。每个演示者都由位于我的MainWindowViewModel 中的属性表示。这也是两位演示者的 IsEnabled 属性所在的位置。

contentPresenters 均使用以下结构创建：UserControl -> ViewModel -> Data Model。

现在我正在尝试通过更改主窗口 ViewModel 中的 IsEnabled 属性来禁用必要的 contentPresenter，方法是从获得焦点的 contentPresenter 的代码隐藏中。

contentPresenter 用户控制代码隐藏：

public partial class EditBlockUC : UserControl
{
    public EditBlockViewModel ViewModel { get { return DataContext as EditBlockViewModel; } }

    public EditBlockUC()
    {
        InitializeComponent();
    }

    //Runs when the user control gets focus
    private void UserControl_GotFocus(object sender, RoutedEventArgs e)
    {
        //This UserControl has access to MainWindowViewModel through
        //it's own ViewModel, EditBlockViewModel         
        ViewModel.MainViewModel.LeftWidgetEnabled = false;
    }
}

该行：ViewModel.MainViewModel.LeftWidgetEnabled = false; 成功更改了主窗口视图模型中的属性，但视图不受影响。我可以通过调用NotifyPropertyChange() 来解决这个问题吗？如果是这样，我该怎么做？

如果这是完全错误的解决方案，请告诉我，并帮助我解决它。

谢谢

更新 1：

我的完整基类：

public class PropertyChangedBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }

    public virtual void NotifyPropertyChange<TProperty>(Expression<Func<TProperty>> property)
    {
        var lambda = (LambdaExpression)property;

        MemberExpression memberExpression;
        if (lambda.Body is UnaryExpression)
        {
            var unaryExpression = (UnaryExpression)lambda.Body;
            memberExpression = (MemberExpression)unaryExpression.Operand;
        }
        else
            memberExpression = (MemberExpression)lambda.Body;

        OnPropertyChanged(memberExpression.Member.Name);
    }

    protected bool SetField<T>(ref T field, T value, string propertyName)
    {
        if (EqualityComparer<T>.Default.Equals(field, value)) return false;
        field = value;
        OnPropertyChanged(propertyName);
        return true;
    }
}

更新 2：

我的LeftWidgetEnabled 属性：

public bool LeftWidgetEnabled
{
    get { return _leftWidgetEnabled; }
    set { SetField(ref _leftWidgetEnabled, value, "LeftWidgetEnabled"); }
}

Answer 1

ViewModel.MainViewModel 类的 LeftWidgetEnabled 必须是这样的：

private bool leftWidgetEnabled;
public bool LeftWidgetEnabled
{
    get { return leftWidgetEnabled; }
    set { SetField(ref leftWidgetEnabled, value, "LeftWidgetEnabled"); }
}

另外，您的MainViewModel 必须实现INotifyPropertyChanged。

您最好让MainViewModel 继承自ViewModelBase 并让ViewModelBase 实现INotifyPropertyChanged。

public class MainViewModel : ViewModelBase
{        
    private bool leftWidgetEnabled;
    public bool LeftWidgetEnabled
    {
        get { return leftWidgetEnabled; }
        set { SetField(ref leftWidgetEnabled, value, "LeftWidgetEnabled"); }
    }
}

public class ViewModelBase : INotifyPropertyChanged
{
    // boiler-plate
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
    protected bool SetField<T>(ref T field, T value, string propertyName)
    {
        if (EqualityComparer<T>.Default.Equals(field, value)) return false;
        field = value;
        OnPropertyChanged(propertyName);
        return true;
    }
}

更新 1

你的 ContentPresenter 应该被绑定如下：

<ContentPresenter IsEnabled="{Binding Path=LeftWidgetEnabled}" />

而UserControl 的DataContext（ContentPresenter 处于打开状态）应该是MainViewModel 的实例。

例如：

<UserControl 
    x:Class="MyApplication.UserControl1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:viewModels="**PATH TO YOUR VIEWMODELS-ASSEMBLY**"
    mc:Ignorable="d">

<UserControl.DataContext>
    <viewModels:MainViewModel />
</UserControl.DataContext>

    <ContentPresenter IsEnabled="{Binding Path=LeftWidgetEnabled}" />
</UserControl>

Answer 2

你实现 INotifyPropertyChanged 如下

class ViewModel : INotifyPropertyChanged
{

  private bool leftWidgetEnabled;
  public bool LeftWidgetEnabled
  {
     get 
      { 
        return leftWidgetEnabled;
      }
      set 
      { 
          leftWidgetEnabled=value
         OnPropertyChanged("LeftWidgetEnabled"); 
      }
   }

    public void OnPropertyChanged(string PropertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}