C# 虚拟财产
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virtual properties
提问by Mackintoast
I have used and learned only virtual methods of the base class without any knowledge of virtual properties used as
我只使用和学习了基类的虚拟方法，而没有任何用作虚拟属性的知识
class A
{
public virtual ICollection<B> prop{get;set;}
}
Could someone tell me what that means ?
有人能告诉我这是什么意思吗？
采纳答案by Zenexer
public virtual ICollection<B> Prop { get; set; }
Translates almost directly to:
几乎直接翻译为：
private ICollection<B> m_Prop;
public virtual ICollection<B> get_Prop()
{
return m_Prop;
}
public virtual void set_Prop(ICollection<B> value)
{
m_Prop = value;
}
Thus, the virtual keyword allows you to override the property in sub-classes just as you would the above get/set methods:
因此，virtual 关键字允许您像上面的 get/set 方法一样覆盖子类中的属性：
public override ICollection<B> Prop
{
get { return null; }
set { }
}
回答by Chriseyre2000
It's a collection that's implementation can vary in a descendant class.
这是一个集合，其实现在后代类中可能会有所不同。
回答by loodakrawa
Properties are a shortened form of accessor methods (Get & Set). That means that the virtual keyword has the same meaning as with any other method. That means you can override it in derived classes.
属性是访问器方法（Get & Set）的缩写形式。这意味着 virtual 关键字与任何其他方法具有相同的含义。这意味着您可以在派生类中覆盖它。
回答by Tarik
Properties are actually specials cases of Getter and Setter methods. So they are like combinations of Getter and Setter methods as shown below:
属性实际上是 Getter 和 Setter 方法的特殊情况。所以它们就像 Getter 和 Setter 方法的组合，如下所示：
private string _name;
public string GetName()
{
return _name;
}
public void SetName(string value)
{
this._name = value;
}
So virtualkeyword is same for properties as well which means it is overrideable by the child classes and initial implementation can be changed.
所以virtual关键字对于属性也是相同的，这意味着它可以被子类覆盖并且可以更改初始实现。
回答by Husein Roncevic
In Entity Framework (which I believe your example refers to), your POCO classes are created and wrapped into a proxy class. Proxy class is a descendant of the class that you declare, so your class A becomes a base class. This proxy class is populated with data and returned back to you. This is necessary in order to track changes. Have a look at this article http://technet.microsoft.com/en-us/query/dd456848
在实体框架（我相信你的例子所指的）中，你的 POCO 类被创建并包装到一个代理类中。代理类是您声明的类的后代，因此您的类 A 成为基类。这个代理类填充了数据并返回给您。这是跟踪更改所必需的。看看这篇文章http://technet.microsoft.com/en-us/query/dd456848
I had a similar problem in trying to understand this and after a few debugging sessions and seeing the proxy classes and reading about tracking changes it made be figure out why it is declared the way it is.
我在尝试理解这一点时遇到了类似的问题，经过几次调试会话并查看代理类并阅读有关跟踪更改的内容后，我才弄清楚为什么它是这样声明的。
回答by Stephane Halimi
You can have methods (often), properties, indexers or events, the virtual keyword has the same meaning : modifying the meaning (override) of the base class item. With properties, you can change the get/set accessors.
您可以拥有方法（通常）、属性、索引器或事件，virtual 关键字具有相同的含义：修改基类项的含义（覆盖）。使用属性，您可以更改 get/set 访问器。
回答by Behnoud Sherafati
In object-oriented programming, a virtual property is a property whose behavior can be overridden within an inheriting class. This concept is an important part of the polymorphism portion of object-oriented programming (OOP).
在面向对象的编程中，虚拟属性是一种可以在继承类中覆盖其行为的属性。这个概念是面向对象编程 (OOP) 多态性部分的重要组成部分。
look at the example below:
看看下面的例子：
public class BaseClass
{
public int Id { get; set; }
public virtual string Name { get; set; }
}
public class DerivedClass : BaseClass
{
public override string Name
{
get
{
return base.Name;
}
set
{
base.Name = "test";
}
}
}
at the presentation level:
在演示级别：
DerivedClass instance = new DerivedClass() { Id = 2, Name = "behnoud" };
Console.WriteLine(instance.Name);
Console.ReadKey();
the output will be "test" because the "Name" property has been overridden in the derived class(sub class).
输出将是“test”，因为“Name”属性已在派生类（子类）中被覆盖。
