1 类和结构,继承和方法复写及扩展方法及部分类

面向对象最重要的元素之一,它是对外部世界的抽象,我们来看一个最标准的类:

     /// <summary>

    /// 一个人

    /// </summary>

    public class People

    {

        /// <summary>

        /// 默认构造函数,建议要有一个

        /// </summary>

        public People()

        {

        }

        /// <summary>

        /// 只初始化人的姓名

        /// </summary>

        /// <param name="name"></param>

        public People(string name)

        {

            this.Name = name;

        }

        /// <summary>

        /// 只初始化人的姓名和性别

        /// </summary>

        /// <param name="name"></param>

        /// <param name="gander"></param>

        public People(string name, bool gander)

            : this(name)

        {

            this.Gander = gander;

        }

        /// <summary>

        /// 只和类本身有关的属性,我们把它做成静态的

        /// </summary>

        public static string ClassName = "人类";

        /// <summary>

        /// 在程序运行期间不变的做为常量

        /// </summary>

        public const double PI = 3.1415926;

        /// <summary>

        /// 姓名

        /// </summary>

        public string Name { get; set; }

        /// <summary>

        /// 性别,1为女,0为男

        /// </summary>

        public bool Gander { get; set; }

        /// <summary>

        /// 身份证

        /// </summary>

        public string NumID { get; set; }

        /// <summary>

        /// 地址

        /// </summary>

        public string Address { get; set; }

        /// <summary>

        /// 年龄

        /// </summary>

        public int Age { get; set; }

}

如果我们希望建立一个叫小明的人,怎么办?

  People 小明 = new People("小明");

  Console.WriteLine(小明.Name + 小明.Gander); //注意bool型默认为False

如果建立一个叫小红的女人,就可以这样了

            People 小红 = new People("小红", true);

            Console.WriteLine(小红.Name +小红.Gander);

OK,这时,我们已经建立了两个人了,我想知道它们的身高体重,怎么办?我们可以想一个人的身高和体重是每个人固有的信息,我们可以把它们放在一个结构里面,就像这样,

/// <summary>

    /// 描述人的身高和体重信息的结构体

    /// </summary>

    public struct HighWeight

    {

        /// <summary>

        /// 只设置身高

        /// </summary>

        /// <param name="height"></param>

        public HighWeight(int high)

            : this()

        {

            this.High = high;

        }

        /// <summary>

        /// 只设置体重

        /// </summary>

        /// <param name="weight"></param>

        public HighWeight(double weight)

            : this()

        {

            this.Weight = weight;

        }

        /// <summary>

        /// 对身高和体重进行初始化

        /// </summary>

        /// <param name="height"></param>

        /// <param name="weight"></param>

        public HighWeight(int height, double weight)

            : this(height)

        {

            this.Weight = weight;

        }

        /// <summary>

        /// 身高

        /// </summary>

        public int High { get; private set; } //private属性只允许类内部对本属性赋值

        /// <summary>

        /// 体重

        /// </summary>

        public double Weight { get; private set; }

}

那我们在调用时,就是这样:

HighWeight heghweight = new HighWeight(175);

Console.WriteLine("身高:{0},体重:{1}", heghweight.High, heghweight.Weight);

HighWeight heghweight2 = new HighWeight(74.4);

Console.WriteLine("身高:{0},体重:{1}", heghweight2.High, heghweight2.Weight);

HighWeight heghweight3 = new HighWeight(175,74.4);

Console.WriteLine("身高:{0},体重:{1}", heghweight3.High, heghweight3.Weight);

事实上,身高体重是属于每个人的一种特性,所以,我们应该把它放在人的类上,于是代码就变成了这样:

     /// <summary>

    /// 一个人

    /// </summary>

    public class People

    {

        /// <summary>

        /// 默认构造函数,建议要有一个

        /// </summary>

        public People()

        {

        }

        /// <summary>

        /// 只初始化人的姓名

        /// </summary>

        /// <param name="name"></param>

        public People(string name)

        {

            this.Name = name;

        }

        /// <summary>

        /// 只初始化人的姓名和性别

        /// </summary>

        /// <param name="name"></param>

        /// <param name="gander"></param>

        public People(string name, bool gander)

            : this(name)

        {

            this.Gander = gander;

        }

        /// <summary>

        /// 只和类本身有关的属性,我们把它做成静态的

        /// </summary>

        public static string ClassName = "人类";

        /// <summary>

        /// 在程序运行期间不变的做为常量

        /// </summary>

        public const double PI = 3.1415926;

        /// <summary>

        /// 姓名

        /// </summary>

        public string Name { get; set; }

        /// <summary>

        /// 性别

        /// </summary>

        public bool Gander { get; set; }

        /// <summary>

        /// 身份证

        /// </summary>

        public string NumID { get; set; }

        /// <summary>

        /// 地址

        /// </summary>

        public string Address { get; set; }

        /// <summary>

        /// 年龄

        /// </summary>

        public int Age { get; set; }

        /// <summary>

        /// 身高和体重

        /// </summary>

        public HighWeight HighWeight { get; set; }

}

继承,这个概念不难理解,它是指一个具有公共对象的类被其它具有相似功能的类继承,其中被继承的类称为基类,所对应的类叫做它的子类,继承在大项目中用的不多,因为继承会增加程序的耦合度(即类之间的相互依赖的程度).回到实例中来,所有人都会运动,无论是爬,走,还是跑,只是根据年龄不同,他们的运动所不同,看代码:

  #region 方法

        public virtual string Run()

        {

            return "刚出生的人只会爬";

        }

  #endregion

上面这段代码是People类的,下面是它的子类,将这个方法进行复写

     /// <summary>

    /// 满1岁的人

    /// </summary>

    public class Yang : People

    {

        /// <summary>

        /// 调用它的父类的构造方法为父类属性赋值

        /// </summary>

        /// <param name="name"></param>

        public Yang(string name)

            : base(name)

        {

        }

        public override string Run()

        {

            return "满一岁,人会走了";

        }

}

下面是对类进行调用的过程:

People p = new People();

Console.WriteLine(p.Run());

Yang yang = new Yang("小孩");

Console.WriteLine("姓名:{0},它的运动:{1}", yang.Name, yang.Run());

接下来,我要说扩展方法了,顾名思义,就是定义在一个类外部的方法,但这个方法又可以作用在这个类上,看代码:

     /// <summary>

    /// 静态类,包括所以类的扩展方法

    /// </summary>

    public static class AllEvent

    {

        /// <summary>

        /// People的扩展方法,方法和方法所在的类必须是static 

        /// </summary>

        /// <param name="people"></param>

        /// <param name="name"></param>

        /// <returns></returns>

        public static People GetPeopleByName(this List<People> people, string name)

        {

            return people.Where(i => i.Name.Equals(name)).SingleOrDefault();

        }

}

调用的时候,可以直接使用它

List<People> peopleList = new List<People>() 

            {

              new People("张三",true),

              new People("李四",false),

            };

      Console.WriteLine(peopleList.GetPeopleByName("李四").Name);

接下来,就是一个概念性的东西, System.Nullable<T>,即可空的类型,它可以叫值类型也赋null这种值,定义如下:

Int? Pi          //定义一个页签变量

Int pi=Pi ?? 1 //如果pi为空,然后将1赋值pi

OK,我们来看一个问题,我们的人类people目前的结果如图

看起来,有点乱了,我们想把它的方法和属性分开,这样做,有两个好像,第一代码清晰,第二也是引用部分类partial的作用,就是有利于团队开发.(check in  and check out )如图:

到些,第一讲就完了!好累呀!