Question

I am using a custom default button attached behaviour (as defined here: Silverlight 4 Default Button Service).

I am able to bind this successfully in XAML, but in a nested user control, in code behind the following does not work:

public partial class MyNestedUserContol{

/// a DP for storing the name of the default button, used in the ElementName binding
public string DefaultButton {
    get { return (string)GetValue(DefaultButtonProperty); }
    set { SetValue(DefaultButtonProperty, value); }
}
public static readonly DependencyProperty DefaultButtonProperty =
    DependencyProperty.Register("DefaultButton", typeof(string), typeof(TeamReferenceFieldEditor), new PropertyMetadata(null));

...

private void CreateCustomControls(){
    ...
    TextBox tb = new TextBox();
    ...
    AddDefaultButtonBinding(tb);
    ...
}

private void AddDefaultButtonBinding(Control control) {
    Binding binding = new Binding();
    binding.ElementName = this.DefaultButton;
    control.SetBinding(DefaultButtonService.DefaultButtonProperty, binding); }

...
}

How should I create the binding for this in code?
Thanks,
Mark

Answer 1

Ultimately this will be a problem in namescopes. The value assigned to ElementName probably doesn’t exist in the same namescope that the TextBox belongs to.

Have you considered simply using:-

 private void MainPage_Load(object sender, RoutedEventArgs e)
 {
   LayoutRoot.AddHandler(UIElement.KeyUpEvent, LayoutRoot_KeyUp, true)
 }

 private void LayoutRoot_Keyup(object sender, KeyEventArgs e)
 {
   if (e.Key == Key.Enter)
   {
     // invoke default operation here
   }
 }

I’ve read through your other question and the blog article. Its seems like a bad smell to have to attach strange properties to various controls like a textbox to implement a default button, which ultimately has nothing to do with the textbox.

It would be a better pattern to attach a property on the button which is to be declared the default (or to create a sub-class of Button called DefaultButton) and to have that co-operate with the containing UserControl, Page or ChildWindow to watch for the enter key. This would not then have to involve other controls not directly related to delivering this functionality.