Force binding update for a TextBox

The TextBox control updates the Text binding source only when it looses focus.

When you are writing in a TextBox and you press a button in the ApplicationBar, the focus not changes and your MVVM property doesn't update.

The workaround is to force the binding update like this:

 
var focusedElement = FocusManager.GetFocusedElement();
var focusedTextBox = focusedElement as TextBox;

if (focusedTextBox != null)
{
    var binding = focusedTextBox.GetBindingExpression(TextBox.TextProperty);
    if (binding != null)
        binding.UpdateSource();
}