1、屬性
所謂屬性其實就是特殊的類別成員，它實作了對私有類別域的受控存取。在C#語言中有兩種屬性方法，其一是get，透過它可以傳回私有域的值，其二是set，透過它就可以設定私有域的值。比如說，以下面的程式碼為例，建立學生姓名屬性，控制對name欄位的受控存取：
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
簡單說來，所謂索引器就是一類特殊的屬性，透過它們你就可以像引用數組一樣引用自己的類別。顯然，這項功能在創建集合類別的場合特別有用，而在其他某些情況下，例如處理大型檔案或抽象某些有限資源等，能讓類別具有類似陣列的行為當然也是非常有用的。例如，上例中，我們假設一個班級有若干個學生，建構索引器就可以很方便地呼叫：
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();
}
}上面程式碼中，我們看到索引器的存取器帶一個參數（參數為整數），其實可以建構多個參數的索引器。也以上述代碼為例，我們要根據學生學號和姓名得到學生的考試總分，修改後代碼如下：
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、總結：
<1>、
屬性的定義：
訪問修飾符傳回型別屬性名稱
｛
get｛語句集合｝
get｛語句集合｝
get｛語句集合｝
set｛語句集合｝
索引器使得物件可依與陣列相似的方法索引。
this 關鍵字用於定義索引器。
get 訪問器傳回值。 set 存取器指派值。
索引器不必根據整數值進行索引，由你決定如何定義特定的查找機制。
索引器可被重載。
a、類別的每個屬性都必須擁有唯一的名稱，而類別裡定義的每一個索引器都必須擁有唯一的簽章（signature）或參數清單（這樣就可以實作索引器重載）。
b、屬性可以是static（靜態的）而索引器則必須是實例成員。
<4>、索引器重載實例：
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();
}
}
