如何：使用自动实现的属性实现轻量类（C# 编程指南）
此示例演示如何创建一个不可变轻量类，用于仅封装一组自动实现的属性。 当您必须使用引用类型语义时，请使用此种构造而不是结构。
请注意：对于自动实现的属性，需要 get 和 set 访问器。 要使该类不可变，请将 set 访问器声明为 private。 但是，声明私有 set 访问器时，不能使用对象初始值来初始化属性。 必须使用构造函数或工厂方法。
示例
下面的示例演示两种方法来实现具有自动实现属性的不可变类。 第一个类使用构造函数初始化属性，第二个类使用静态工厂方法。
// This class is immutable. After an object is created,
// it cannot be modified from outside the class. It uses a
// constructor to initialize its properties.
class Contact
{
// Read-only properties.
public string Name { get; private set; }
public string Address { get; private set; }
// Public constructor.
public Contact(string contactName, string contactAddress)
{
Name = contactName;
Address = contactAddress;
}
}
// This class is immutable. After an object is created,
// it cannot be modified from outside the class. It uses a
// static method and private constructor to initialize its properties.
public class Contact2
{
// Read-only properties.
public string Name { get; private set; }
public string Address { get; private set; }
// Private constructor.
private Contact2(string contactName, string contactAddress)
{
Name = contactName;
Address = contactAddress;
}
// Public factory method.
public static Contact2 CreateContact(string name, string address)
{
return new Contact2(name, address);
}
}
public class Program
{
static void Main()
{
// Some simple data sources.
string[] names = {"Terry Adams","Fadi Fakhouri", "Hanying Feng",
"Cesar Garcia", "Debra Garcia"};
string[] addresses = {"123 Main St.", "345 Cypress Ave.", "678 1st Ave",
"12 108th St.", "89 E. 42nd St."};
// Simple query to demonstrate object creation in select clause.
// Create Contact objects by using a constructor.
var query1 = from i in Enumerable.Range(0, 5)
select new Contact(names[i], addresses[i]);
// List elements cannot be modified by client code.
var list = query1.ToList();
foreach (var contact in list)
{
Console.WriteLine("{0}, {1}", contact.Name, contact.Address);
}
// Create Contact2 objects by using a static factory method.
var query2 = from i in Enumerable.Range(0, 5)
select Contact2.CreateContact(names[i], addresses[i]);
// Console output is identical to query1.
var list2 = query2.ToList();
// List elements cannot be modified by client code.
// CS0272:
// list2[0].Name = "Eugene Zabokritski";
// Keep the console open in debug mode.
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
}
/* Output:
Terry Adams, 123 Main St.
Fadi Fakhouri, 345 Cypress Ave.
Hanying Feng, 678 1st Ave
Cesar Garcia, 12 108th St.
Debra Garcia, 89 E. 42nd St.
*/
编译器为每个自动实现的属性创建了后备字段。 这些字段无法直接从源代码进行访问。