Question

I’m having one hell of a time trying to get my databinding to work correctly. I have reason to believe that what I’m trying to accomplish can’t be done, but we’ll see what answers I get.

I’ve got a UserControl. This UserControl contains nothing more than a button. Now within the code behind, I’ve got a property name IsBookmarked. When IsBookmarked is set, code is run that animates the look of the button. The idea is that you click the button and it visually changes. We’ll call this UserControl a Bookmark control.

Now I have another control, which we’ll call the FormControl. My FormControl contains a child Bookmark control. I’ve tried to do databinding on my Bookmark control, but it’s not working. Here’s some code to help you out.

This is the XAML and Loaded event handler of my control. As you can see it contains a child element that is a custom control (bookmark). So once this control loads, it’s DataContext is set to an new instance of an Employee object. Silverlight also sets the DataContext property of my child bookmark control to the same instance. I’ve verified this by debugging. If my parent has a valid DataContext set then why can’t my child control (bookmark) property databind to it?

<UserControl ......>
    <q:Bookmark x:Name="BookMarkControl1" IsBookmarked="{Binding IsSiteBookmarked}" />
</UserControl>

public void Control_Loaded(object sender, EventArgs e)
{
    DataContext = new Employee { IsSiteBookmarked = True };

}

This is my custom control below. Obviously it contains more than this, but for readability I’ve trimmed it down to the property I’m trying to databind to.

//this is the bookmark control. I've included this control within another control, and I'm trying to databind to properties within my parents DataContext
public partial class Bookmark : UserControl
{

    bool _IsBookmarked= false;
    public bool IsBookmarked
    {
        get {return _IsBookmarked;}
        set { 
                 _IsBookmarked= value;
                 SwitchMode(value);
            }
    }

}

UPDATE

Got some javascript errors that I should mention. Firebug reports a AG_E_PARSER_BAD_PROPERTY_VALUE exception. It doesn’t seem like my databinding is even working yet.

Answer 1

Make your IsBookmarked property on the Bookmark control a dependency property.

I presume Control_Loaded is a part of your FormControl, in which case I’m not sure you are using DataContext properly. Best double check that.

UPDATE: Yes, you are using the DataContext properly. AG_E_PARSER_BAD_PROPERTY_VALUE indicates you need to make the IsBookmarked property a dependency property, like so:

 Public Property IsBookmarked() As Boolean
    Get
        Return Me.GetValue(IsBookmarkedProperty)
    End Get
    Set(ByVal value As Boolean)
        Me.SetValue(IsBookmarkedProperty, value)
    End Set
End Property

Public Shared ReadOnly IsBookmarkedProperty As DependencyProperty = DependencyProperty.Register("IsBookmarked", GetType(Boolean), GetType(Bookmark), New PropertyMetadata(New PropertyChangedCallback(AddressOf OnIsBookmarkedPropertyChanged)))

Private Shared Sub OnIsBookmarkedPropertyChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
    Dim cntrl As Bookmark = TryCast(d, Bookmark)
    cntrl.SetIsBookmarked(e.NewValue)
End Sub

If you only need to store the value for later use, then you don’t need to do anything in the OnIsBookmarkedPropertyChanged procedure, But I put some code there as an example anyway.

Good Luck!