WPF使用覆盖属性在XAML类继承 [英] WPF use override Property in inherit class in XAML

问题描述

我有一个小问题，不容找到任何解决方案。也许这是在Visual Studio中的一个问题。

I have a little problem and can´t find any solution. Maybe it is an issue in Visual Studio.

我创建了一个从图片继承一个新的类。然后我重写Source属性。

I have created a new class that is inherited from Image. I then override the Source property.

class GifImage : Image
{
     public new ImageSource Source
     {
         get { return base.Source; } 
         set
         {
             MesssageBox("new source property");
             base.Source = value;
         } 
     }
}

如果我在代码中设置源

GifImage gifImage = new GifImage();
gifImage.Source = gifimage2;

那么源将被正确设置为GifImage和消息框将显示。

Then the Source will be correctly set to GifImage and the MessageBox will be shown.

但是，如果我在XAML的代码集来源：

But if I set Source in the Xaml-Code:

<my1:GifImage Stretch="Uniform" Source="/WpfApplication1;component/Images/Preloader.gif" />

然后将图像的来源属性将设置并在MessageBox不需额外显示。

Then the Source property of the Image will be set and the MessageBox won´t be shown.

我的想法是设置System.ComponentModel.Browsable属性，认为也许在继承GifImage类的属性不是在Visual Studio中可见，它是使用source属性父类的。

My idea was to set the System.ComponentModel.Browsable-Attribute, thinking that maybe the property in the inherit GifImage class is not visible in Visual Studio and it is using the source property of the parent class.

[Browsable(true)]
public new ImageSource Source

但是，这仍然没有工作。

But this is still not working.

有人偷了同样的问题和/或该解决方案？

Has somebody had the same problem or/and the solution for this?

推荐答案

您无法在WPF的方式来覆盖的DependencyProperty。

You are not able to override a DependencyProperty in that manner in WPF.

作为图像源属性是一个的DependencyProperty，当值在XAML（和其他地方）被分配它的值用

As the Source property on an Image is a DependencyProperty, when the value is assigned in XAML (and other places) it's value is set using

DependencyObject.SetValue(SourceProperty, value)

一个可能的解决方案是重写DependencyProperty的元数据，并添加更改侦听器，如：

One possible solution is to override the metadata of the DependencyProperty and add change listener, e.g.

    static GifImage()
    {
        SourceProperty.OverrideMetadata(typeof(GifImage), new FrameworkPropertyMetadata(new PropertyChangedCallback(SourcePropertyChanged)));

    }

    private static void SourcePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
    {
        MessageBox("new source property");
    }

或alternativly使用DependencyPropertyDescriptor

or alternativly using the DependencyPropertyDescriptor

DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(Image.SourceProperty, typeof(Image));
if (dpd != null)
{
   dpd.AddValueChanged(tb, delegate
   {
       MessageBox("new source property");
   });
}

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