C# 类 class

类是使用关键字 class 声明的,如下面的示例所示:

class TestClass
{
    // Methods, properties, fields, events, delegates 
    // and nested classes go here.
}
 

下面的示例说明如何声明类的字段、构造函数和方法。该例还说明了如何实例化对象及如何打印实例数据。在此例中声明了两个类,一个是 Child 类,它包含两个私有字段(nameage)和两个公共方法。第二个类 TestClass 用来包含 Main

class Child
{
    private int age;
    private string name;

    // Default constructor:
    public Child()
    {
        name = "N/A";
    }

    // Constructor:
    public Child(string name, int age)
    {
        this.name = name;
        this.age = age;
    }

    // Printing method:
    public void PrintChild()
    {
        Console.WriteLine("{0}, {1} years old.", name, age);
    }
}

class StringTest
{
    static void Main()
    {
        // Create objects by using the new operator:
        Child child1 = new Child("Craig", 11);
        Child child2 = new Child("Sally", 10);

        // Create an object using the default constructor:
        Child child3 = new Child();

        // Display results:
        Console.Write("Child #1: ");
        child1.PrintChild();
        Console.Write("Child #2: ");
        child2.PrintChild();
        Console.Write("Child #3: ");
        child3.PrintChild();
    }
}
/* Output:
    Child #1: Craig, 11 years old.
    Child #2: Sally, 10 years old.
    Child #3: N/A, 0 years old.
*/

注意:在上例中,私有字段(nameage)只能通过
Child 类的公共方法访问。例如,不能在 Main
方法中使用如下语句打印 Child 的名称:

Console.Write(child1.name);   // Error

 

posted @ 2013-01-23 13:50  447726527  阅读(274)  评论(0编辑  收藏  举报
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