I want to share this great post from Anoop that shows a easy way to add a notification system to dependency properties of a given element. It creates and attaches a new property to the existing property and let’s you specify the PropertyChangedCallback eventhandler.
There are different examples on the internet, but i like how Anoop created a generic method with access to the callback event handler.
Here is the main part of the code:
/// Listen for change of the dependency property
public void RegisterForNotification(string propertyName, FrameworkElement element, PropertyChangedCallback callback)
{
//Bind to a depedency property
Binding b = new Binding(propertyName) { Source = element };
var prop = System.Windows.DependencyProperty.RegisterAttached(
"ListenAttached"+propertyName,
typeof(object),
typeof(UserControl),
new System.Windows.PropertyMetadata(callback)); element.SetBinding(prop, b);
}
And here is an example on how to use it:
//Shows a message box when the text of the Textbox changes.
RegisterForNotification
("Text", this.txtMain,(d,e)=>MessageBox.Show("Text changed"));
Read Anoop’s complete article for more information!
update (07/28/2011):
here is small update of the code so it also works with other objects instead of just FrameworkElements
private void RegisterForNotification(string propertyName, object source, PropertyChangedCallback callback)
{
Binding b = new Binding(propertyName);
b.Source = source; DependencyProperty prop = System.Windows.DependencyProperty.RegisterAttached(
"ListenAttached" + propertyName,
typeof(object),
this.GetType(),
new System.Windows.PropertyMetadata(callback)); BindingOperations.SetBinding(this, prop, b);
}
引用
Tips & Tricks: Listening to Dependency Property change notifications of a given Element