网站建设衤金手指花总十四/互联网营销师培训课程

类与结构的区别
C++中结构与类的唯一区别是在于默认的访问级别，但是C#中的区别就稍微多了点，C#中如下
(1)类是引用类型，结构是值类型。
类中：

public class Person
{public string Name { get; set; }public int Age { get; set; }public Person(string name, int age){Name = name;Age = age;}
}class Program
{static void Main(){Person person1 = new Person("Leopold", 6);Console.WriteLine("person1 Name = {0} Age = {1}", person1.Name, person1.Age);// Declare  new person, assign person1 to it.Person person2 = person1;//Change the name of person2, and person1 also changes.person2.Name = "Molly";person2.Age = 16;Console.WriteLine("person2 Name = {0} Age = {1}", person2.Name, person2.Age);Console.WriteLine("person1 Name = {0} Age = {1}", person1.Name, person1.Age);// Keep the console open in debug mode.Console.WriteLine("Press any key to exit.");Console.ReadKey();}
}

    Output:
    person1 Name = Leopold Age = 6
    person2 Name = Molly Age = 16
    person1 Name = Molly Age = 16

结构中：

public struct Person
{public string Name;public int Age;public Person(string name, int age){Name = name;Age = age;}
}public class Application
{static void Main(){// Create  struct instance and initialize by using "new".// Memory is allocated on thread stack.Person p1 = new Person("Alex", 9);Console.WriteLine("p1 Name = {0} Age = {1}", p1.Name, p1.Age);// Create  new struct object. Note that  struct can be initialized// without using "new".Person p2 = p1;// Assign values to p2 members.p2.Name = "Spencer";p2.Age = 7;Console.WriteLine("p2 Name = {0} Age = {1}", p2.Name, p2.Age);// p1 values remain unchanged because p2 is  copy.Console.WriteLine("p1 Name = {0} Age = {1}", p1.Name, p1.Age);// Keep the console open in debug mode.Console.WriteLine("Press any key to exit.");Console.ReadKey();}
}

  Output:
    p1 Name = Alex Age = 9
    p2 Name = Spencer Age = 7
    p1 Name = Alex Age = 9
(2)结构中可以包含构造函数，但是构造函数必须对全部字段赋值，因此结构没有默认构造函数
(3)结构不能被继承，但是结构可以实现接口
(4)结构直接继承自 System.ValueType，类继承自 System.Object
(5)结构中除非是const或者static变量，或者不能直接对变量初始化

namespace ConsoleApplication5
{struct struct1{//int x = 10;		//errorint x;string str;//struct1(){}		//error//struct1(int _x)	//error//{ x = _x; }struct1(int _x, string _str){x = _x;str = _str;}const int y = 10;	//OKstatic int z = 100;	//OK}
}

(6)结构可以是Nullable类型
所谓的Nullable类型就是System.Nullable<T>的实例，它的取值范围是值类型T可以表达的所有有效值 外加一个null值。
Nullable存在的意义：值类型必须初始化后才能使用，为了让值类型不用初始化，就诞生了这个类型了。