Comments on: Silverlight Attached Properties: Binding.UpdateSourceTrigger.PropertyChanged

By: Keith

Keith — Tue, 29 Jun 2010 23:22:48 +0000

Ugh… I guess it’s the HTML killing it… Should inherit from generic Behavior where T is TextBox.

By: Keith

Keith — Tue, 29 Jun 2010 23:21:50 +0000

Sorry, error above due to trying to “fix” formatting. Should inherit from : Behavior not just Behavior.

By: Keith

Keith — Tue, 29 Jun 2010 23:20:43 +0000

Here it is as a behavior:

public class PropertyChangedBindingBehavior : Behavior
{
protected override void OnAttached()
{
base.OnAttached();

AssociatedObject.TextChanged += new TextChangedEventHandler(AssociatedObject_TextChanged);
}

protected override void OnDetaching()
{
base.OnDetaching();

AssociatedObject.TextChanged -= new TextChangedEventHandler(AssociatedObject_TextChanged);
}

void AssociatedObject_TextChanged(object sender, TextChangedEventArgs e)
{
AssociatedObject.GetBindingExpression(TextBox.TextProperty).UpdateSource();
}
}

You need a reference to System.Windows.Interactivity.

Then in XAML:

i is the System.Windows.Interactivity, beh is your namepsace for the PropertyChangedBindingBehavior.

I think it’s nicer than the attached property since you can unwire from the TextChanged.

By: Karin

Karin — Mon, 07 Sep 2009 09:07:41 +0000

Thanks a lot for your article! This is exactly what I was looking for. I just replaced the part that changes the focus by a call to the UpdateSource method of the binding expression:

if ((bool)e.NewValue)
{
textBox.TextChanged += (s, arg) =>
{
textBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();
};
}

By: dennis

dennis — Wed, 19 Aug 2009 14:48:46 +0000

Hi,

I am just curious? does XAML on silverlight doesnt have any
UpdateSourceTrigger on binding? say UpdateSourceTrigger=PropertyChanged…

Why do you need to get the parent control?
and why do loop on visual tree to get the parent control?

I think there is a simple way to get the parent control using
XAML and no need for code behind..

By: blackjack2150

blackjack2150 — Tue, 04 Aug 2009 07:41:08 +0000

Hi.
Thanks for this post. It works fine for me, but I still feel a bit awkward knowing how it actually does.
I’m currently working with Silverlighlt 3 and Prism and I can’t help notice the paradox: we use this separation paterns (MVVM for me)in order to keep the code clear and easy to test, modify, etc, but in order to make it actually work, there are a lot of dirty hacks that must be implemented, some with unpredictible side effects. The ideas are great, but the technology is still lacking…

By: Jeremiah Morrill

Jeremiah Morrill — Thu, 30 Jul 2009 17:12:53 +0000

I was using this method for a minute (so thanks for getting me out of a jam!), but then I found a _cleaner_ way to implement, that is compatible with SL3.

private static void OnUpdateSourceTriggerChanged(DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
var textBox = d as TextBox;

if (textBox == null)
return;

KeyEventHandler textChanged = (s, arg) =>
{
BindingExpression bindingExpression = textBox.GetBindingExpression(TextBox.TextProperty);

bindingExpression.UpdateSource();
};

if ((bool)e.NewValue)
{
textBox.KeyDown -= textChanged;
}

if ((bool)e.NewValue)
{
textBox.KeyDown += textChanged;
}
}

By: Thomas Claudius Huber

Thomas Claudius Huber — Fri, 17 Jul 2009 12:07:26 +0000

Hi Michael,

great post. I’ve another solution that doesn’t need the focus trick. Take a look at my blog: http://www.thomasclaudiushuber.com/blog/2009/07/17/here-it-is-the-updatesourcetrigger-for-propertychanged-in-silverlight/