一个WPF派生的依赖属性可能吗?

I want to expose a property that is a string format of two other dependency properties. How do I make this work so anything bound to the derived property is also updated when the true dependency property is updated?

我想公开一个属性，它是另外两个依赖项属性的字符串格式。如何使此工作有效，以便当真正的依赖项属性被更新时，绑定到派生属性的任何内容也被更新?

public static readonly DependencyProperty DeviceProperty =
    DependencyProperty.Register("Device", typeof(string), typeof(SlaveViewModel));

public static readonly DependencyProperty ChannelProperty =
    DependencyProperty.Register("Channel", typeof(Channels), typeof(SlaveViewModel));

public string Device
{
    get { return (string)GetValue(DeviceProperty); }
    set { SetValue(DeviceProperty, value); }
}

public Channels Channel
{
    get { return (Channels)GetValue(ChannelProperty); }
    set { SetValue(ChannelProperty, value); }
}

Now I would like to be able to bind to the following derived property and have it treated as a dependency property:

现在我希望能够绑定到以下派生属性并将其作为依赖属性处理:

public string DeviceDisplay
{
    get 
    {
        return string.Format("{0} (Ch #{1})", Device, (int)Channel);
    }
}

I'm able to do this by adding callbacks. It works well but it seems a bit verbose. Is there an easier way to do this other than the following?

我可以通过添加回调来实现这一点。它工作得很好，但似乎有点啰嗦。除了下面的方法，还有其他更简单的方法吗?

public static readonly DependencyProperty DeviceProperty =
    DependencyProperty.Register("Device", typeof(string), typeof(SlaveViewModel),
    new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.None,
    new PropertyChangedCallback(OnDevicePropertyChanged)));

private static void OnDevicePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
    SlaveViewModel model = (SlaveViewModel)sender;
    model.DeviceDisplay = string.Format(string.Format("{0} (Ch #{1})",
        args.NewValue, (int)model.Channel));
}

public static readonly DependencyProperty ChannelProperty =
    DependencyProperty.Register("Channel", typeof(Channels), typeof(SlaveViewModel),
    new FrameworkPropertyMetadata(Channels.Channel1, FrameworkPropertyMetadataOptions.None,
    new PropertyChangedCallback(OnChannelPropertyChanged)));

private static void OnChannelPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
    SlaveViewModel model = (SlaveViewModel)sender;
    model.DeviceDisplay = string.Format(string.Format("{0} (Ch #{1})",
        model.Device, (int)args.NewValue));
}

public static readonly DependencyPropertyKey DeviceDisplayPropertyKey =
    DependencyProperty.RegisterReadOnly("DeviceDisplay", typeof(string),
    typeof(SlaveViewModel), new FrameworkPropertyMetadata(""));

public static readonly DependencyProperty DeviceDisplayProperty =
    DeviceDisplayPropertyKey.DependencyProperty;  

public string DeviceDisplay
{
    get { return (string)GetValue(DeviceDisplayProperty); }
    protected set { SetValue(DeviceDisplayPropertyKey, value); }
}

1 个解决方案

#1

I see copy-pasted code, you can just point both callbacks to a single method. Do not know if there is an easier way, but i doubt it.

我看到了复制粘贴的代码，您可以将两个回调都指向一个方法。不知道有没有更简单的办法，但我怀疑。

(Also the typeof(SlaveViewModel) suggests that this is VM code: I for one would never use DPs in a VM because of thread-affinity.)

(SlaveViewModel)的类型也表明，这是VM代码:对于一个人来说，由于线程亲和性的原因，我永远不会在VM中使用DPs。)

#1