[WPF系列]基础 Listening to Dependency Property change notifications of a given Element

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