NP104 Why is rule not followed1?

June 27, 2008

Hi Guys

NP104 Why is rule not followed1?

It should be like this:

AddBookEventHandler bookShop.AddBook +=

new AddBookEventHandler(notify.instance_AddBook);

But in the following program it is like this:

bookShop.AddBook +=

new AddBookEventHandler(notify.instance_AddBook);

But program is executing well.   

Please explain the reason.

Thank you

using System;

using System.Collections;

namespace Events

{

    public delegate void AddBookEventHandler(object source, BookEventArgs e);

    public class Book

    {

        private string title;

        private string isbn;

        private decimal price;

        public Book(string title, string isbn, decimal price)

        {

            this.title = title;

            this.isbn = isbn;

            this.price = price;

        }

        public string Title

        {

            get { return this.title; }

        }

        public string ISBN

        {

            get { return this.isbn; }

        }

        public decimal Price

        {

            get { return this.price; }

        }

    }

    public class BookShop

    {

        private ArrayList books;

        private string name;

        public event AddBookEventHandler AddBook;

        public BookShop(string name)

        {

            books = new ArrayList();

            this.name = name;

        }

        protected void OnAddBook(BookEventArgs e)

        {

            if (AddBook != null)

                AddBook(this, e);

        }

        public void AddNewBook(Book book)

        {

            this.books.Add(book);

            BookEventArgs e = new BookEventArgs(book);

            OnAddBook(e);

        }

    }

    public class BookEventArgs : EventArgs

    {

        private Book book;

        public BookEventArgs(Book book)

        {

            this.book = book;

        }

        public Book Book

        {

            get { return this.book; }

        }

    }

    public class Notifier

    {

        public void instance_AddBook(object source, BookEventArgs e)

        {

            Console.WriteLine("A Message has been sent to the Members\n" + " regarding the book '{0}' with the ISBN '{1}'\n", e.Book.Title, e.Book.ISBN);

        }

    }

    //The Sys Class is the application that uses all the above classes.

    //Let's look at the code:

    public class Sys

    {

        public static void Main()

        {

            BookShop bookShop = new BookShop(".NET Bookshop");

            Book b1 = new Book("The Right Way", "123456789", 19.90m);

            Book b2 = new Book("The .NET Stuff", "987654321", 29.90m);

            Notifier notify = new Notifier();

            bookShop.AddBook += new

              AddBookEventHandler(notify.instance_AddBook);

            bookShop.AddNewBook(b1);

            bookShop.AddNewBook(b2);

            Console.ReadLine();

        }

    }

}