构造函数与析构函数:
using System; class MyClass { private int FNum; public int Num { get { return FNum; } } /* 构造函数没有返回值, 无参的构造函数是默认的 */ public MyClass() { this.FNum = 2009; } /* 可以有多个参数不同的构造函数 */ public MyClass(int x) { this.FNum = x; } public MyClass(params int[] arr) { foreach (int i in arr) this.FNum += i; } /* 析构函数无参、无返回值、无访问修饰, 最多只能有一个 */ ~MyClass() { //析构函数是自动调用的 } } class Program { static void Main() { MyClass obj1, obj2, obj3; obj1 = new MyClass(); Console.WriteLine(obj1.Num); //2009 obj2 = new MyClass(100); Console.WriteLine(obj2.Num); //100 obj3 = new MyClass(1, 2, 3); Console.WriteLine(obj3.Num); //6 Console.ReadKey(); } }
如果没有构造与析构函数, new 时将使用默认(或继承); 给一个私有的构造函数能阻止类被实例化:
using System; class MyClass { private MyClass() { } public static void Msg1() { Console.WriteLine("Msg1"); } public static void Msg2() { Console.WriteLine("Msg2"); } } class Program { static void Main() { MyClass.Msg1(); //Msg1 MyClass.Msg2(); //Msg2 Console.ReadKey(); } }
如果一个类有了非默认的构造函数, 就不能再使用默认的构造函数:
using System; class MyClass { private int FNum; public int Num { get { return FNum; } } public MyClass(int x, int y) { this.FNum = x + y; } } class Program { static void Main() { MyClass obj; obj = new MyClass(1, 2); Console.WriteLine(obj.Num); //3 Console.ReadKey(); } }
静态构造函数:
静态构造函数既无访问修饰符、无参数;
在 new 或调用任何静态成员之前,将自动调用静态构造函数;
静态构造函数一般用于初始化静态数据;
静态构造函数会在第一次 new 或第一次使用静态成员前触发;
不能直接调用静态构造函数.
using System; class MyClass { public static int Num; public static void ShowNum() { Console.WriteLine(Num); } public void Msg() { Console.WriteLine("Msg"); } static MyClass() { Num = 123; } } class Program { static void Main() { MyClass.ShowNum(); //123 MyClass.Num = 2009; MyClass.ShowNum(); //2009 MyClass obj1 = new MyClass(); obj1.Msg(); //Msg Console.ReadKey(); } }
自动调用父类的构造方法:
using System; class Parent { public Parent() { Console.WriteLine("Parent"); } } class Child1 : Parent { public Child1() { Console.WriteLine("Child1"); } public Child1(int x) { Console.WriteLine(x); } } class Child2 : Child1 { public Child2() { Console.WriteLine("Child2"); } public Child2(int x, int y) { Console.WriteLine(x + y); } } class Program { static void Main() { Parent p = new Parent(); // Parent Child1 c1 = new Child1(); // Parent / Child1 Child2 c2 = new Child2(); // Parent / Child1 / Child2 Child1 c11 = new Child1(999); // Parent / 999 Child2 c22 = new Child2(111, 222); // Parent / Child1 / 333 Console.ReadKey(); } }
base:
using System; class Parent { public Parent() { Console.WriteLine("Parent"); } public Parent(int x, int y) { Console.WriteLine(x + y); } public Parent(string s1, string s2) { Console.WriteLine(s1 + s2); } } class Child1 : Parent { public Child1() { Console.WriteLine("Child1"); } } class Child2 : Parent { public Child2() : base() { Console.WriteLine("Child2"); } } class Child3 : Parent { public Child3() : base(111,222) { Console.WriteLine("Child3"); } } class Child4 : Parent { public Child4() : base("111", "222") { Console.WriteLine("Child4"); } } class Program { static void Main() { Child1 c1 = new Child1(); // Parent / Child1 Child2 c2 = new Child2(); // Parent / Child2 Child3 c3 = new Child3(); // 333 / Child3 Child4 c4 = new Child4(); // 111222 / Child4 Console.ReadKey(); } }
this:
using System; class MyClass { private string fs = "ABC-"; public MyClass() { Console.WriteLine("MyClass"); } public MyClass(string str) { Console.WriteLine(this.fs + str); } public MyClass(int num) : this() { Console.WriteLine(num); } public MyClass(int x, int y) : this("XYZ") { Console.WriteLine(x + y); } } class Program { static void Main() { MyClass c1 = new MyClass(); // MyClass MyClass c2 = new MyClass("EFG"); // ABC-EFG MyClass c3 = new MyClass(123); // MyClass / 123 MyClass c4 = new MyClass(111, 222); // ABC-XYZ / 333 Console.ReadKey(); } }
构造函数、属性、base:
using System; abstract class Parent { private byte FID; public Parent(byte n) { FID = n; } public byte Id { get { return FID; } set { FID = value; } } } class Child : Parent { public Child(byte MyID) : base(MyID) { } } class Program { static void Main() { Child Rect = new Child(6); Console.WriteLine(Rect.Id); //6 Rect.Id = 8; Console.WriteLine(Rect.Id); //8 Console.ReadKey(); } }