CODEWITHSUNDEEP
c#wpfdependency-properties
It'sNotALie.
It'sNotALie.

Reputation: 22814

How are you meant to declare a Dependency Property?

I was reading a tutorial on how to make a parametrized style (here). In it, it uses some dependency properties. It declares them as such:

public static Brush GetTickBrush(DependencyObject obj)
{
    return (Brush)obj.GetValue(TickBrushProperty);
}
public static void SetTickBrush(DependencyObject obj, Brush value)
{
    obj.SetValue(TickBrushProperty, value);
}
public static readonly DependencyProperty TickBrushProperty =
    DependencyProperty.RegisterAttached(
        "TickBrush",
        typeof(Brush),
        typeof(ThemeProperties),
        new FrameworkPropertyMetadata(Brushes.Black));

Now, as I like snippets, I went ahead and looked for one, to see if I didn't have to make one. There was one, but in a completely different style:

public int MyProperty
{
    get { return (int)GetValue(MyPropertyProperty); }
    set { SetValue(MyPropertyProperty, value); }
}
// Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty MyPropertyProperty = 
    DependencyProperty.Register("MyProperty", typeof(int), typeof(ownerclass), new PropertyMetadata(0));

Now, what I don't get: what's the difference between these two? Why does one need a DependencyObject to get the value while the other one doesn't? Do you use them in separate scenarios?

Upvotes: 3

Views: 459

Answers (1)

O. R. Mapper
O. R. Mapper

Reputation: 20760

The first example you show is for an attached property, which is a special kind of a dependency property. Values of attached properties can be "attached" to other objects, while usual dependency properties belong to the instances of their respective class.

The second code snippet shows a regular dependency property and is the way to go if you just want to add an additional dependency property to a custom class you are creating.

Upvotes: 4

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