依賴屬性命令的 CanExecute() 未更新

Question

我有一個用戶控件，並在其中定義了以下屬性：

public string MyProperty
{
      get { return (string)GetValue(MyPropertyProperty); }
      set { SetValue(MyPropertyProperty, value); }
}
        
public static readonly DependencyProperty MyPropertyProperty =
      DependencyProperty.Register("MyProperty", typeof(string),
           typeof(MyUserControlView), new PropertyMetadata(null, MyPropertyChangedCallback));

private static void MyPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
     var control = (MyUserControl) d;
     control.MyProperty = (string)e.NewValue;
}

和以下命令：

public ICommand MyCommand
{
     get { return (ICommand)GetValue(MyCommandProperty); }
     set { SetValue(MyCommandProperty, value); }
}

public static readonly DependencyProperty MyCommandProperty =
     DependencyProperty.Register("MyCommand", typeof(ICommand), typeof(MyUserControlView),
         new PropertyMetadata(null, MyCommandPropertyChangedCallback));

private static void MyCommandPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
     var control = (MyUserControlView)d;
     control.MyCommand = (DelegateCommand)e.NewValue;
}

void ExecuteMyCommand() {...}

bool CanExecuteMyCommand(){
    return !string.IsNullOrWhiteSpace(MyProperty);
}

我初始化這個命令

SetValue(MyCommandProperty, new DelegateCommand(ExecuteMyCommand, CanExecuteMyCommand));

問題是CanExecuteMyCommand()方法不起作用，因為它不使用MyProperty的當前值。 為什么會這樣？如何在用戶控件中正確使用我的命令？

Answer 1

您必須在更改MyProperty后調用CanExecuteChanged ，它將調用CanExecute 。