构造函数

构造函数是在第一次创建对象时调用的方法。构造函数具有与类相同的名称，它通常用于初始化对象的数据。
不带参数的构造函数称为默认构造函数。构造函数中的代码都在创建新对象时候执行。
下面看一个默认构造函数的列子：
class Book
    {
        private string title;
        private string author;
        private double price;
        public Book()
        { //默认的构造函数
            title = "asp.net从入门到精通";
            author = "aliang";
        }
        public double BookPrice
        {
            get { return price ;}
            set { price=value*2;}
        }
        public string BookInfo
        {
            get { return "书的名称是：" + title + "<br>" + "书的作者是：" + author+"<br>"; }
       
        }
    }
    protected void Page_Load(object sender, EventArgs e)
    {
         Book mybook = new Book();
        mybook.BookPrice = 19.98;
        Response.Write(mybook.BookInfo);
        Response.Write("书的价格是："+mybook.BookPrice);

    }
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下面看一个带参数的构造函数的例子

 class Book
    {
        private string title;
        private string author;
        private double price;
        public Book(string newtitle,string newauthor)
        { //带参数的构造函数，它通常用于初始化对象的数据。
            title = newtitle;
            author =newauthor;
        }
        public double BookPrice
        {
            get { return price ;}
            set { price=value*2;}
        }
        public string BookInfo
        {
            get { return "书的名称是：" + title + "<br>" + "书的作者是：" + author+"<br>"; }
       
        }
    }
    protected void Page_Load(object sender, EventArgs e)
    {
    
        Book mybook = new Book("ASP.NET2.0从入门到精通","aliang");//注意这里，是带参数的。因为构造函数是带参数的。
        mybook.BookPrice = 19.98;
        Response.Write(mybook.BookInfo);
        Response.Write("书的价格是："+mybook.BookPrice);
        Response.Write("<hr>");

        Book mybook1 = new Book("SQL2005学习指南", "JHON");
        mybook1.BookPrice = 45.88;
        Response.Write(mybook1.BookInfo);
        Response.Write("书的价格是：" + mybook1.BookPrice);

  

    }