UserControl中的DependencyProperty

Question

I'm creating a UserControl "UC". I have my class with data "AClass". I want an object of this class to be a DP in my UserControl. So i put the definition in UC:

public static readonly DependencyProperty AProperty =
    DependencyProperty.Register("A", typeof(AClass),
    typeof(UC), new FrameworkPropertyMetadata(new AClass()));

public AClass A
{
    get { return (AClass)GetValue(AProperty); }
    set { SetValue(AProperty, value); }
}    

Here's how I create my control in XAML:

xmlns:l="clr-namespace:MyWorkspace"
// ...
<Grid>
    <l:UC Height="100" Width="150" Activity="{Binding a}" />
</Grid>

I defined "a" in the code-behind file:

public partial class MainWindow : Window
{
    public AClass a {get; set;}
    public MainWindow()
    {
        DataContext = this;
        a = // create an object
        InitializeComponent();
    }
}

Next, in my UC I want to refer to "A" and use one of its property:

private void DoSomethingInUC()
{
   int size = A.AsProperty;
   // ...
}

The problem is that every time I refer to "A" it is uninitialized (ie "AsProperty" contains default value).

What's wrong in that ?

Answer 1

1) How can your A DP be of type double and AClass?

2) You most likely want to avoid doing this :

new FrameworkPropertyMetadata(new AClass())

because the exact AClass instance you new up right there will be shared as default by all of your UserControl instances.

3) You have to make your MainWindow implement INotifyPropertyChanged (prefer making a MainWindowViewModel) and have your a property RaisePropertyChanged inside it's setter.