Accessibility Level

◎ 常見的存取修飾詞

• Private : 僅可以在該 CLASS 中使用，通常在 FIELD 設為 PRIVATE
• Public : 最開放的存取修飾詞
• Protected : 僅限於 父類別 以及其 子類別使用
• Internal : 僅能被使用於目前的 Assembly ( 該專案編譯產生的 .dll 或 .exe )
• Protected Internal : 同時有 Protected 與 Internal 的性質

◎ Assembly ?

在範例之前，我們先來了解什麼是 Assembly 一般來說新增一個「類別庫(Class Library)」專案之後

「專案」上按下右鍵-->屬性
重新建置之後...

◎ 範例程式碼

一般的主控台應用程式(要加入類別庫的參考)

using System;
using OnlineGame;
using static  System.Console;

namespace AccessModifiersDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            Gamer gamer = new Gamer();
            //int gamer_gameScore = gamer._gameScore; // Error, Not available.
            //int gamer_Level = gamer._level; // Error, Not available.
            WriteLine("gamer.GameScore == {0}", gamer.GameScore);
            GamerSub gamerSub = new GamerSub();
            gamerSub.GetGameScore();
            WriteLine("gamerSub.GameScore == {0} , gamerSub.Level = {1}.", gamerSub.GameScore, gamerSub.Level);

            WriteLine("============ 範例二 ============");

            //GamerA gamerA = new GamerA();
            ////int gamerA_gameScore = gamerA._gameScore; // Error, Not available.
            ////int gamerA_Level = gamerA._level; // Error, Not available.
            //Console.WriteLine("gamerA.GameScore == {0}", gamerA.GameScore);
            //GamerASub gamerASub = new GamerASub();
            //Console.WriteLine("gamerASub.Level == {0} , gamerASub.GameScore = {1}", gamerASub.GameScore, gamerASub.Level);
            //// gamerASub.GetGameScore();   // Error, Not available.
            Console.ReadLine();
        }
    }
}

namespace OnlineGame
{
    public class Gamer
    {
        #region Field
        private int _gameScore = 0;
        protected int _level = 1;
        #endregion
        #region Property
        public int GameScore
        {
            get
            {
                return _gameScore;
            }
            set
            {
                _gameScore = value;
            }
        }
        #endregion
    }
    //Internal 代表僅能被使用於目前的 Assembly ( 該專案編譯產生的 dll 或 exe )
    internal class GamerSub : Gamer
    {
        #region Property
        //用Property方式讓子類別可以存取父類別的 Protected Field
        public int Level
        {
            get
            {
                return base._level;
            }
            set
            {
                base._level = value;
            }
        }
        #endregion
        #region  Function
        public int GetGameScore()
        {
            //使用父類別的Property，存取
            return base.GameScore;
        }
        #endregion
    }
}

類別庫程式碼

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace OnLineGameA
{
    public class GamerA
    {
        // private field means only available in current class.
        private int _gameScore = 500;
        // protected field means available in current class and its sub class.
        protected internal int _level = 2;
        // public property means available every where.
        public int GameScore
        {
            get
            {
                return _gameScore;
            }
            set
            {
                _gameScore = value;
            }
        }
    }
    //Internal means only available in current assembly.
    public class GamerASub : GamerA
    {
        #region Property
        //用Property方式讓子類別可以存取父類別的 Protected Field
        public int Level
        {
            get
            {
                return _level;
            }
            set
            {
                _level = value;
            }
        }
        #endregion
        // Protected internal method means only available in current assembly, and its sub class.
        protected internal int GetGameScore()
        {
            ////return base._gameScore;
            //  base._gameScore is private, thus, not available in its sub class.
            return GameScore;
        }
    }
}