[Abstract] design pattern difference method and virtual methods

1. abstract methods

It can only be defined in an abstract class

Modifier measures can not be modified private virtual static

Abstract method is as follows:

public abstract class People   //声明一个抽象类
{
   public abstract void study();  //抽象方法只能定义在抽象类中。
}
public class Student:People   //继承抽象类
{
     public  override void study()     //重写抽象类的抽象方法
     {
            Console.WriteLine("好好学习，天天向上!");
     }
}
public class Program
{
    static void Main(string[] args)
{
      Student t= new Student();//实例化派生类
      People  p= t;   //使用派生类对象实例化抽象类
       //以上两句等价于  
      //People p = new Student();//使用派生类对象实例化抽象类；
      p.study(); //使用抽象类对象调用抽象类中的抽象方法study    
}
}

to sum up: 

(1) can only be declared abstract method in an abstract class, use the keyword abstract

(2) The abstract class abstract method must be overridden by subclasses .

[Abstract method is not a method thereof, a method thereof subclasses must override !!, abstract method thus can be seen as a virtual method is not the method body]

 

Virtual methods:

Modified using virtual methods:

Virtual method can be a method thereof. Specific examples are as follows:

public class BaseClass         //创建一个基类
{
    public virtual string GetName()    //使用virtual关键字创建父类中的虚方法
    {
             return "父类虚方法体":     
     }
}
public class SubClass:BaseClass    //子类继承父类
{
     public override string GetName();   //子类重写父类虚方法
      {
               return "重写父类虚方法!";
       }
}

Example above: virtual methods of the parent class is a derived class overrides.

Note: virtual modifier can not be used in conjunction with private, static, abstract, override modifier.

ps: override modifier and not new, static, virtual modifier used simultaneously, and only overridden method in the base class virtual method for rewriting.

 

 

Third, the difference between the two:

Summary: The abstract method is only a method name, there is no way the body (that is, no specific implementation method), subclass the parent class abstract method must be rewritten;

           This method is a virtual function member has a method, but subclasses can cover, may not be covered.

(1) The method of virtual methods thereof, the method is not an abstract method thereof. Abstract method is a method of covering the derived class forced, or derived class can be instantiated;

(2) only abstract method declarations in an abstract class, not a virtual method;

(3) derived class must override the abstract method of the abstract class, a virtual method is not necessary.