你的位置:首页 > ASP.net教程

[ASP.net教程]const 和 readonly 修饰符的用法


1. 只有C#内置类型(int,double,long等)可以声明为const;结果、类和数组不能声明为const。

2. readonly 是在字段上使用的修饰符,直接以类名.字段访问。

3. const 必须在申明中初始化。之后不能再修改。

4. readonly可以在申明中初始化,也可以在构造函数中初始化,其它情况不能修改。

namespace const_and_readonly{  class Program  {    static void Main(string[] args)    {      Console.WriteLine("Half a year have {0} Moths", Calendar.Moths/2); //直接类名.字段访问const字段      Calendar test1 = new Calendar();      Console.WriteLine("Every year has {0} weeks and {1} days", test1._weeks, test1._days);//readonly字段通过实例访问      Calendar test2 = new Calendar(31, 4);      Console.WriteLine("January has {0} weeks and {1} days", test2._weeks ,test2 ._days);      Console.ReadKey();    }  }  class Calendar  {    public const int Moths = 12; //const必须在声明中初始化    public readonly int _days=365;  //readonly在声明中初始化    public readonly int _weeks;    public Calendar()          //readonly在构造函数内初始化    {      _weeks = 52;    }    public Calendar(int days,int weeks) //readonly在构造函数内初始化    {      _days = days;      _weeks = weeks;    }    public void setvalue(int days,int weeks)    {      // _days = days; 无法对只读字段赋值      //_weeks = weeks; 无法对只读字段赋值    }  }