Use extension methods to check BlackboardNotes (or events)

This is a simple example, but it demonstrates how extension methods can make your classes smaller and easier to read.

As seen in the RPG demo project (CreationPortraitImages.cs & CreationExtensions.cs), when a BlackboardNote is passed to a ReceiveChange() method, we can sipmly call something very easy to read:

public override void ReceiveChange(BlackboardNote blackboardNote)
{
     if (blackboardNote.IsNewActorSelected())
          UpdatePortrait();
}

In this code, IsNewActorSelected() is an extension method for BlackboardNote objects. Check CreationExtensions.cs to see the code:

public static bool IsNewActorSelected(this BlackboardNote note)
{
    return note.topic == gameData.activePlayerTopic &&
        note.subject == gameData.activePlayerSubject;
}

In the demo project, we know that the BlackboardNote which contains the active player information will only be updated (and sent as a notitication) when it changes. So this extension method returns true if the topic and subject of the BlackboardNote match the topic and subject we have hard coded in the gameData class.