ChangeAwareContentControl–How to know when the content changes in a ContentControl

I am working on an application where I have a ContentControl, and I need to know when the content changes. My initial thought was to add an event handler for the ContentChanged event. I came to find out that the ContentControl does not fire a ContentChanged event.

My solution was to create a control derived from content control that fires that particular event. It is working quite nicely, so I thought I would share. I hope it helps you out. It’s a small amount of code, but it does the trick.

    public class ChangeAwareContentControl : ContentControl
    {
        static ChangeAwareContentControl()
        {
            ContentProperty.OverrideMetadata(typeof(ChangeAwareContentControl),
                new FrameworkPropertyMetadata(
                    new PropertyChangedCallback(OnContentChanged)));
        }

        private static void OnContentChanged(DependencyObject d,
            DependencyPropertyChangedEventArgs e)
        {
            ChangeAwareContentControl mcc = d as ChangeAwareContentControl;
            if (mcc.ContentChanged != null)
            {
                DependencyPropertyChangedEventArgs args
                    = new DependencyPropertyChangedEventArgs(
                        ContentProperty, e.OldValue, e.NewValue);
                mcc.ContentChanged(mcc, args);
            }
        }

        public event DependencyPropertyChangedEventHandler ContentChanged;
    }

Here is how you use it in xaml.

<controls:ChangeAwareContentControl ContentChanged="ContenChangedHandler"/>

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