c# 第三课 类

类： 其中的成员变量和成员函数有public,private,protected,internal,protected internal五种

Access-modifiers；

public : the type or member can be  accessed by any other code in the same assembly or another assembly that reference it.

private : the type or member can only be accessed by code in the same class or struct.

protected : the type or member can only be accessed by code in the same or struct, or in a derived class. 

internal : the type or member can be accessed by any code in the same assembly,but not from another assembly.

protected internal : the type or member can be accessed by any code in the same assembly, or by any derived class in another assembly.

深拷贝和浅拷贝：

对于类来说，浅拷贝只是拷一个指针。拷贝与被拷贝的内容占用同一片内存区域，删除一个变量时，另一个变量也为空。深拷贝则是重新开辟一块内存区域。两片内存区域存相同的内容。删除其中一个变量时，对另一个变量没有影响。

this 关键字：refers to the current instance of an object. used in 5 ways.

1 public void SomeMethod(int hour)

{

this.hour = hour;

}

2 class myClass

{

    public void Foo(otherClass otherObject)

    {

       otherObject.bar(this);

    }

}

3 with indexers

4 to call oneoverloaded constructor from another

  class myClass

  {

      public myClass(int i)

      public myClass():this(42)

  }

5 to explicitly invoke methods and members of a class, as a form of documentation:

public void Method(int y)

{

   int x = 0;

   x = 7;

   y = 8;

   this.z = 5;

   this.Draw();

}

 

静态类不能实例化

静态类是密封的，不能从它派生类型

静态类不能包含非静态成员，也不能有构造方法。

面向对象的三个特点：封装，多态，继承。