Behavior to force TextBox model update to prevent trouble with the ApplicationBar - Init

<body> <h1>Behavior to force TextBox model update to prevent trouble with the ApplicationBar</h1> <p><a href="http://feedads.g.doubleclick.net/~a/awJbhqOklnbg_onQmat9LdcDq_E/0/da"><img src="http://feedads.g.doubleclick.net/~a/awJbhqOklnbg_onQmat9LdcDq_E/0/di" border="0" ismap="true"></img></a><br/> <a href="http://feedads.g.doubleclick.net/~a/awJbhqOklnbg_onQmat9LdcDq_E/1/da"><img src="http://feedads.g.doubleclick.net/~a/awJbhqOklnbg_onQmat9LdcDq_E/1/di" border="0" ismap="true"></img></a></p><p>A small quicky this time:</p> <p>Problem:</p> <ul> <li>TextBox, Text property bound to a string in my ViewModel <li>I type text in the TextBox <li>I click a “Save” button on my ApplicationBar <li>The string in my ViewModel is not updated. It never gets updated. WTF???</li></ul> <p>It appears the TextBox only updates it’s value to a bound string when it loses focus. And a TextBox does not lose focus when you click an ApplicationBar Button. Meh.</p> <p>I have found a few solutions and workarounds, and in the end rolled my own:  a very small behavior that updates the binding every time you type something in your textbox. That’s a bit wasteful, but it works for me. It builds on the <a href="http://dotnetbyexample.blogspot.com/2011/11/safe-event-detachment-base-class-for.html" target="_blank">SafeBehavior</a> pattern I wrote about earlier, and it’s so small I post it in one go:</p><pre>using System.Windows.Controls; namespace Wp7nl.Behaviors { /// <summary> /// A behavior to for text box model update when text changes /// </summary> public class TextBoxChangeModelUpdateBehavior : SafeBehavior<TextBox> { protected override void OnSetup() { AssociatedObject.TextChanged += AssociatedObjectTextChanged; } protected override void OnCleanup() { AssociatedObject.TextChanged -= AssociatedObjectTextChanged; } void AssociatedObjectTextChanged(object sender, TextChangedEventArgs e) { var binding = AssociatedObject.GetBindingExpression(TextBox.TextProperty); if (binding != null) { binding.UpdateSource(); } } } }</pre> <p>I have read amongst other things Prism has a UpdateTextBindingOnPropertyChanged behavior. Well this one will be in the next version of my <a href="http://twitter.com/#!/search/%23wp7nl" target="_blank">#<a href="http://wp7nl.codeplex.com/" target="_blank">wp7nl library on codeplex</a> </a></p> <div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/5295746446529817470-4265293998871597340?l=dotnetbyexample.blogspot.com' alt='' /></div><img src="http://feeds.feedburner.com/~r/blogspot/dotnetbyexample/~4/c3_IJFJGA_Y" height="1" width="1"/> </body>