1、属性
所谓属性其实就是特殊的类成员，它实现了对私有类域的受控访问。在C#语言中有两种属性方法，其一是get，通过它可以返回私有域的值，其二是set，通过它就可以设置私有域的值。比如说，以下面的代码为例，创建学生姓名属性，控制对name字段的受控访问：
using System;
public class Student
{
private string name;
/// <summary>
/// 定义学生的姓名属性
/// </summary>
public string Name
{
get { return name; }
set { name = value; }
}
}
class Program
{
static void Main(string[] args)
{
Student student = new Student();
student.Name = "Jeff Wong";
Console.WriteLine(student.Name);
Console.Read();
}
}2、索引器
简单说来，所谓索引器就是一类特殊的属性，通过它们你就可以像引用数组一样引用自己的类。显然，这一功能在创建集合类的场合特别有用，而在其他某些情况下，比如处理大型文件或者抽象某些有限资源等，能让类具有类似数组的行为当然也是非常有用的。比如，上例中，我们假设一个班级有若干个学生，构建索引器就可以很方便地调用：
using System;
using System.Collections.Generic;
public class Student
{
public List<Student> listStudents = new List<Student>();
/// <summary>
/// 构建索引器
/// </summary>
/// <param name="i"></param>
/// <returns></returns>
public Student this[int i]
{
get { return listStudents[i]; }
set { listStudents[i] = value; }
}
private string name;
/// <summary>
/// 属性
/// </summary>
public string Name
{
get { return name; }
set { name = value; }
}
public Student(string name)
{
this.name = name;
}
public Student()
{
this.listStudents.Add(new Student("jeff wong"));
this.listStudents.Add(new Student("jeffery zhao"));
this.listStudents.Add(new Student("terry lee"));
this.listStudents.Add(new Student("dudu"));
}
}
class Program
{
static void Main(string[] args)
{
Student student = new Student();
int num = student.listStudents.Count;
Console.WriteLine("All the students:");
for (int i = 0; i < num; i++)
{
Console.WriteLine(student[i].Name); //通过索引器，取所有学生名
}
//设置索引器的值
student[0].Name = "jeff";
Console.WriteLine("After modified,all the students:");
for (int i = 0; i < num; i++)
{
Console.WriteLine(student[i].Name);
}
Console.Read();
}
}上面代码中，我们看到索引器的访问器带一个参数（参数为整数），其实可以构建多个参数的索引器。还以上述代码为例，我们要根据学生学号和姓名得到学生的考试总分，修改后代码如下：
using System;
using System.Collections.Generic;
public class Student
{
public List<Student> listStudents = new List<Student>();
public Student this[int i,string name]
{
get
{
foreach (Student stu in listStudents.ToArray())
{
if (stu.sid == i && stu.name == name) //按照学号和姓名取出学生
{
return stu;
}
}
return null;
}
set { listStudents[i] = value; }
}
private int sid; //学号
public int Sid
{
get { return sid; }
set { sid = value; }
}
private string name;//姓名
public string Name
{
get { return name; }
set { name = value; }
}
private int score; //总分
public int Score
{
get { return score; }
set { score = value; }
}
public Student(int sid, string name, int score)
{
this.sid = sid;
this.name = name;
this.score = score;
}
public Student()
{
this.listStudents.Add(new Student(1, "jeff wong", 375));
this.listStudents.Add(new Student(2,"jeffery zhao",450));
this.listStudents.Add(new Student(3,"terry lee",400));
this.listStudents.Add(new Student(4,"dudu",500));
}
}
class Program
{
static void Main(string[] args)
{
Student student = new Student();
Student stu = student[1, "jeff wong"];
Console.WriteLine("student number:" + stu.Sid + ",name:" + stu.Name + ",score:" + stu.Score);
Console.Read();
}
}3、总结：
<1>、
属性的定义：
访问修饰符 返回类型 属性名
｛
get｛语句集合｝
set｛语句集合｝
｝
索引器的定义：
访问修饰符 返回类型 this[参数类型 参数...]
｛
get｛语句集合｝
set｛语句集合｝
｝
<2>、
索引器使得对象可按照与数组相似的方法进行索引。
this 关键字用于定义索引器。
get 访问器返回值。set 访问器分配值。
value 关键字用于定义由 set 索引器分配的值。
索引器不必根据整数值进行索引，由你决定如何定义特定的查找机制。
索引器可被重载。
<3>、属性和索引器的主要区别：
a、类的每一个属性都必须拥有唯一的名称，而类里定义的每一个索引器都必须拥有唯一的签名（signature）或者参数列表（这样就可以实现索引器重载）。
b、属性可以是static（静态的）而索引器则必须是实例成员。
<4>、索引器重载实例：
using System;
using System.Collections.Generic;
public class Student
{
public List<Student> listStudents = new List<Student>();
public Student this[int i,string name]
{
get
{
foreach (Student stu in listStudents.ToArray())
{
if (stu.sid == i && stu.name == name) //按照学号和姓名取出学生
{
return stu;
}
}
return null;
}
set { listStudents[i] = value; }
}
/// <summary>
/// 索引器重载
/// </summary>
/// <param name="i"></param>
/// <returns></returns>
public Student this[int i] //i从0开始
{
get { return listStudents[i]; }
set { listStudents[i] = value; }
}
private int sid; //学号
public int Sid
{
get { return sid; }
set { sid = value; }
}
private string name;//姓名
public string Name
{
get { return name; }
set { name = value; }
}
private int score; //总分
public int Score
{
get { return score; }
set { score = value; }
}
public Student(int sid, string name, int score)
{
this.sid = sid;
this.name = name;
this.score = score;
}
public Student()
{
this.listStudents.Add(new Student(1, "jeff wong", 375));
this.listStudents.Add(new Student(2,"jeffery zhao",450));
this.listStudents.Add(new Student(3,"terry lee",400));
this.listStudents.Add(new Student(4,"dudu",500));
}
}
class Program
{
static void Main(string[] args)
{
Student student = new Student();
Student stu = student[1, "jeff wong"];
Console.WriteLine("student number:" + stu.Sid + ",name:" + stu.Name + ",score:" + stu.Score);
Console.WriteLine("all the students:");
for (int i = 0; i < student.listStudents.Count; i++)
{
Console.WriteLine("student number:" + student[i].Sid + ",name:" + student[i].Name + ",score:" + student[i].Score);
}
Console.Read();
}
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