How does WPF determine what property to set when setting the content of elements in XAML?

问题

I hope my title is clear....

What I mean is for exmaple when we define animation:

Xaml:

<StoryBoard>
    <DoubleAnimation..../>
</StoryBoard>

But if we defines same thing in code-behind, we could do:

DoubleAnimation myDAnimation = new DoubleAnimation();
.....
StoryBoard myStoryBoard = new StoryBoard();
myStoryBoard.Children.Add(myDAnimation);

I tried to look into StoryBoard's class definition, nothing special:

public sealed class Storyboard : Timeline
{
        public Storyboard();

        // Summary:
        //     Gets the collection of child System.Windows.Media.Animation.Timeline objects.
        //
        // Returns:
        //     The collection of child System.Windows.Media.Animation.Timeline objects.
        //     The default is an empty collection.
        public TimelineCollection Children { get; }
....
}

I know if I defines my own class with the above sytnax, in order to add into my Children, I would need to:

XAML:

<MyClass>
   <MyClass.Children>
      <MyClassCildrenItem..../>
   </MyClass.Children>
</MyClass>

So how did the Xaml knows the DoubleAnimation is should add into StoryBoard's Children property? If I need to do the same thing, what do I need to declare?

回答1:

There's an attribute for that: ContentPropertyAttribute

If you check the Syntax section of classes on MSDN you can see what properties will be set when specifying content. E.g. the ContentControl targets the Content property.

回答2:

TimelineGroup an ancestor of Storyboard has the Children property and it also has the ContentPropertyAttribute which specifies the Children property as the content property.

来源：https://stackoverflow.com/questions/9761574/how-does-wpf-determine-what-property-to-set-when-setting-the-content-of-elements

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