C#构造函数
一、C#构造函数？Construct,Function构造函数是一种特殊的成员函数,它主要用于为对象分配存储空间,对数据成员进行初始化.
构造函数具有一些特殊的性质:
(1)构造函数的名字必须与类同名;
(2)构造函数没有返回类型,它可以带参数,也可以不带参数;
(3)声明类对象时,系统自动调用构造函数,构造函数不能被显式调用;
(4)构造函数可以重载,从而提供初始化类对象的不同方法;
(5)若在声明时未定义构造函数,系统会自动生成默认的构造函数,此时构造函数的函数体为空.
(6)静态构造函数,用static修饰，用于初始化静态变量，一个类只允许有一个构造函数，在类实例化时加载，这时修饰符public、private失去作用.
(7)可以使用public、protected、private修饰符。.
(8)引用父类构造时用（）：base（）方法，引用自身重载的构造使用（）：this（int para）.
(7)可以使用public、protected、private修饰符。
注意：
1、定义了一个带参构造函数后，最好定义一个无参构造函数，这样可以避免子类调用时出错
2、调用基类构造函数：base() 或 ：base(参数列表) 调用本类其它构造函数 ：this() 或 ：this(参数列表)
3、只有在用base显示调用父类的构造函数时，程序才不会默认的调用不带参数的构造函数。
二、C#构造函数的结构层次关系或者说执行顺序是怎样的？Layer,Transfer,Execute
从基类开始构造对象。
public class MyBaseClass
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gifhttp://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public MyBaseClass()
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine("In MyBaseClass()");
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public MyBaseClass(int i)
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine("In MyBaseClass(int i)");
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public class MyDerivedClass : MyBaseClass
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public MyDerivedClass()
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gifhttp://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif http://www.cnblogs.com/Images/dot.gif{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine("In MyDerivedClass()");
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public MyDerivedClass(int i)
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine("In MyDerivedClass(int i)");
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //public MyDerivedClass(int i, int j)
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //{
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif // Console.WriteLine("In MyDerivedClass(int i,int j)");
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //}
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif public MyDerivedClass(int i, int j)
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif : base(i)
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine("In MyDerivedClass(int i,int j):base(i)");
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif class Program
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif static void Main(string[] args)
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http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //Event1
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif MyDerivedClass myObj1 = new MyDerivedClass();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //Event2
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif MyDerivedClass myObj2 = new MyDerivedClass(4);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif //Event3
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif MyDerivedClass myObj3 = new MyDerivedClass(4,8);
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.WriteLine();
http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif Console.ReadKey();
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif }
程序输出：
In MyBaseClass()
In MyDerivedClass()
In MyBaseClass()
In MyDerivedClass(int i)
In MyBaseClass(int i)
In MyDerivedClass(int i,int j):base(i)
很明显，只有在用base显示调用父类的构造函数时，程序才不会默认的调用不带参数的构造函数。
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