class 與struct 區別

      1.class爲引用類型，基類爲system.Object ,struct爲值類型，基類爲system.ValueType,(system.ValueType爲引用類型)

       2.class可以聲明無參構造函數，可以聲明析構函數；而struct只能聲明帶參數構造函數，且不能聲明析構函數。因此，struct沒有自定義的默認無參構造函數，默認無參構造器只是簡單地把所有值初始化爲它們的0等價值

    3.實例化時，class要使用new關鍵字；而struct可以不使用new關鍵字，如果不以new來實例化struct，則其所有的字段將處於未分配狀態，直到所有字段完成初始化，否則引用未賦值的字段會導致編譯錯誤。

     4。• class實例由垃圾回收機制來保證內存的回收處理；而struct變量使用完後立即自動解除內存分配。

　　• 作爲參數傳遞時，class變量是以按址方式傳遞；而struct變量是以按值方式傳遞的。 

 

class Program
    {
        static void Main(string[] args)
        {
            //不使用NEW來生成
            Farmily myfarmily;
            myfarmily.name = "anytao farmily";
            myfarmily.sex = true;
            Console.WriteLine(myfarmily.name);
            //使用new來生成
            Farmily newfarmily=new Farmily("anytao farmily",26,true,"china",new Person("anytao",26));
            Person p = new Person();
            p.Name = "anytao";
            //按值傳遞參數
            ShowFarmily(newfarmily);
            //按引用傳遞參數
            ShowPerson(p);
            newfarmily.GetSex();
            newfarmily.ShowPerson();

            Console.WriteLine(newfarmily.name);
            Console.WriteLine(p.Name);
            Console.WriteLine(newfarmily.ToString());
        }


        public static void ShowPerson(Person p)
        {
            p.Name = "ggg";
            Console.WriteLine("This is {0}", p.Name);
        }

        public static void ShowFarmily(Farmily myfarmily)
        {
            myfarmily.name = "ttt";
            Console.WriteLine("This is {0}",myfarmily.name);
        }
    }

    struct Farmily:IPerson
    {
        public string name;
        public int age;
        public bool sex;
        public string country;
        public Person person;

        //帶參數的構造函數
        public Farmily(string name,int age,bool sex,string country,Person person)
        {
            this.name = name;
            this.age = age;
            this.sex = sex;
            this.country = country;
            this.person = person;
        }




        #region IPerson 成員

        public void GetSex()
        {
            if (sex)
                Console.WriteLine(person.Name + "is a boy");
            else
                Console.WriteLine(person.Name+"is a gril");
        }

        #endregion



        public void ShowPerson()
        { 
            Console.WriteLine("This is {0} from {1}", new Person(name, 22).Name, country);
        }   
        //可以重載ToString虛方法   
        public override string ToString()    
        {   
            return String.Format("{0} is {1}, {2} from {3}", person.Name, age, sex ? "Boy" : "Girl", country);    
        }
    }
    //定義類
    public class Person
    {
        public Person()
        { 
        
        }


        //帶參數的構造函數
        public Person(string name, int age)
        {
            _name = name;
            _age = age;
        }


        private string _name;

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }
        private int _age;

        public int Age
        {
            get { return _age; }
            set { _age = value; }
        }

    }