As you know a FrameworkElement has a property of type ResourceDictionary named Resources, in XAML we can declare it easily like this:
<FrameworkElement.Resources>
<SomeObject x:Key="someKey"/>
<SomeOtherObject x:Key="someOtherKey"/>
</FrameworkElement.Resources>
It's some kind of implicit syntax, all the elements declared inside will be added to the ResourceDictionary. Now I would like to create an attached property having type of ResourceDictionary, of course a requirement of being notified when the property is changed is needed. Here is the code:
public static class Test
{
public static readonly DependencyProperty TestProperty =
DependencyProperty.RegisterAttached("Test", typeof(ResourceDictionary),
typeof(Test), new PropertyMetadata(propertyChanged));
public static ResourceDictionary GetTest(DependencyObject o)
{
return o.GetValue(TestProperty) as ResourceDictionary;
}
public static void SetTest(DependencyObject o, ResourceDictionary resource)
{
o.SetValue(TestProperty, resource);
}
static void propertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
}
}
Usage in XAML:
<Grid>
<local:Test.Test>
<Style TargetType="Button" x:Key="cl"></Style>
</local:Test.Test>
</Grid>
Now if I run the code, an exception will be thrown saying Test property is null. I've tried providing a default instance for the attached property like this:
public static readonly DependencyProperty TestProperty =
DependencyProperty.RegisterAttached("Test", typeof(ResourceDictionary),
typeof(Test), new PropertyMetadata(new ResourceDictionary(), propertyChanged));
Then it seems to run OK but there is not any change notification initially. It's very important to get the change notification at first so that I can proceed some handling.
Currently to achieve what I want, I have to let the default value as null and use it in XAML like this:
<local:Test.Test>
<ResourceDictionary>
<Style TargetType="Button" x:Key="cl"></Style>
</ResourceDictionary>
</local:Test.Test>
That works but not very convenient, I would like it to behave like what we can do with the Resources property of FrameworkElement.
I hope someone here has some suggestion to solve this issue. I would be highly appreciated to receive any idea even something saying it's impossible (but of course you should be sure about that).
