private static void CreateBookAndGetStatistics()
{
// The reference to this assembly allows me to use this class to introduce
// speech into my program. It is loaded by the dynamic language runtime
// when the class is requested
//SpeechSynthesizer speech = new SpeechSynthesizer();
//speech.Speak("Hello, welcome to this stupid gradebook program");
GradeBook book = new GradeBook();
try
{
Console.Write("Enter a name: ");
// Ideally, you should not set the Name property until after you know you have
// a valid value. You could do this by using a combination of a variable
// and a loop which keeps prompting the user until they enter a valid value
// and then, once they do, you are good to store the value of that variable
// into the Name property
book.Name = Console.ReadLine();
}
// Catch blocks can be chained and the first one to match will be the one that
// executes and all the others will be skipped. Thus, include the most specific
// exception blocks first.
catch (ArgumentException ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine(ex.StackTrace);
}
// The Exception type is the most general, from which most others inherit, so it
// comes last. There are only a few which it cannot catch. These are the ones
// that are guaranteed to crash your program. Catching one this general could
// be dangerous since you don't know what kind of exception it is.
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
// Finally is good to add at the end to clean up any resources, regardless
// of wheather or not there is an exception thrown.
book.NameChanged = new NameChangedDelegate(OnNameChanged);
//book.NameChanged = OnNameChanged; // sugar!
// This is legal for delegates. But, if it were an event, you couldn't do this.
// Usually, you should prefer events to provide encapsulation. Events bascially
// translate into a private delegate behind the scenes which only publiclly expose
// subscribe (+=) and unsubscripe (-=) methods.
//book.NameChanged = OnNameChanged2; This will overwrite the delegate, effectively removing all subscribers.
//book.NameChanged("Hehehehe", "I'm invoking the delegate directly from outside the class");
book.NameChanged += OnNameChanged2; // This creates a multicast delegate.
book.NameChanged -= OnNameChanged2; // Removes it from the multicast delegate
// Events:
book.NameChangedEvent += OnNameChanged;
// You can only subscribe and unsubscribe from events. you cannot
// invoke or assign to them directly but only from within the methods
// of the class.
//book.NameChangedEvent("This is no longer legal", "Compile Error!!!!");
//book.NameChangedEvent = null; // Compile error!!
// Events using convention with the title.
book.TitleChanged += OnTitleChanged;
book.Title = "Title";
// This will invoke the set method on the Name property, passing in
// "Jeff's Grade Book" as the "value".
book.Name = "Jeff's Grade Book";
book.AddGrade(81); // 81 is converted to a float
book.AddGrade(75);
book.AddGrade(91.5f);
// book.AddGrade(53.4); // Compile error, cannot convert double to float.
GradeStatistics stats = book.ComputeStatistics();
WriteResult("Average", stats.AverageGrade); // calls the one with a float result
WriteResult("Highest", (int)stats.HighestGrade); // calls the one with a int result (it truncates)
WriteResult("Lowest", stats.LowestGrade);
// You can't do this because you are in a static method. Non-static fields
// and methods are implicitly passed 'this', which is a reference to the
// object calling the method, which you don't have in a static method and
// therefore cannot pass to the non-static method or field. In short, if you
// are in a static method, you can only access other static methods/properties.
//MyProperty = 3;
}