当构造一个c#对象时,理解对象的字段和构造函数的顺序是非常重要的:

1. Derived static fields//派生类静态字段
2. Derived static constructor//派生来静态构造函数
3. Derived instance fields//派生类实例字段
4. Base static fields//基类静态字段
5. Base static constructor//基类静态构造函数
6. Base instance fields//基类实例字段
7. Base instance constructor//基类实例构造函数
8. Derived instance constructor//派生类实例构造函数

下面是简单的代码:

 1

using

 System;

 2

 3

namespace

 ObjectInit

 4

{

 5    class Program

 6    {

 7        static void Main( string[] args )

 8        {

 9            Derived d = new Derived();

10            Console.ReadLine();

11        }

12    }

13    class Base

14    {

15        public Base()

16        {

17            Console.WriteLine( "Base.Instance.Constructor" );

18            this.m_Field3 = new Tracker( "Base.Instance.Field3″ );

19            this.Virtual();

20        }

21        static Base()

22        {

23            Console.WriteLine( "Base.Static.Constructor" );

24        }

25        private Tracker m_Field1 = new Tracker( "Base.Instance.Field1″ );

26        private Tracker m_Field2 = new Tracker( "Base.Instance.Field2″ );

27        private Tracker m_Field3;

28        static private Tracker s_Field1 = new Tracker( "Base.Static.Field1″ );

29        static private Tracker s_Field2 = new Tracker( "Base.Static.Field2″ );

30        virtual public void Virtual()

31        {

32            Console.WriteLine( "Base.Instance.Virtual" );

33        }

34    }

35    class Derived : Base

36    {

37        public Derived()

38        {

39            Console.WriteLine( "Derived.Instance.Constructor" );

40            this.m_Field3 = new Tracker( "Derived.Instance.Field3″ );

41        }

42        static Derived()

43        {

44            Console.WriteLine( "Derived.Static.Constructor" );

45        }

46        private Tracker m_Field1 = new Tracker( "Derived.Instance.Field1″ );

47        private Tracker m_Field2 = new Tracker( "Derived.Instance.Field2″ );

48        private Tracker m_Field3;

49        static private Tracker s_Field1 = new Tracker( "Derived.Static.Field1″ );

50        static private Tracker s_Field2 = new Tracker( "Derived.Static.Field2″ );

51        override public void Virtual()

52        {

53            Console.WriteLine( "Derived.Instance.Virtual" );

54        }

55    }

56    class Tracker

57    {

58        public Tracker( string text )

59        {

60            Console.WriteLine( text );

61        }

62    }

63}

64

65

下面是程序执行结果:

Derived.Static.Field1

Derived.Static.Field2

Derived.Static.Constructor

Derived.Instance.Field1

Derived.Instance.Field2

Base.Static.Field1

Base.Static.Field2

Base.Static.Constructor

Base.Instance.Field1

Base.Instance.Field2

Base.Instance.Constructor

Base.Instance.Field3

Derived.Instance.Virtual

Derived.Instance.Constructor

Derived.Instance.Field3

C#对象初始化的原则 :

• Fields then Constructor.  //先初始化字段,后执行构造函数.
• Static then Instance. //在第一次访问类时,先初始化静态字段和构造函数,后初始化对象的实例字段和构造函数.
• Derived then Base. // 不论字段还是静态构造函数,派生类对象总是先于基类对象初始化.
• Except Instance Constructors.  //对于实例构造函数,基类构造函数总是先于派生类的实例构造函数初始化.
• Don't Assume Field Order.  //字段的初始化顺序总是按照他们在源文件的定义顺序执行的.
• Two-Phase for Virtual. //避免从构造函数中调用虚拟方法.