为什么我需要的是通过公共财产暴露私有字段？ [英] Why do I need a private field that is exposed via public property?

问题描述

我是从Java世界正在添加为主。因此，C＃性能也好看。

I'm comming from Java world mainly. So, C# properties do look nice.

我知道，与C＃3.0或以上，我可以使用自动属性。我更加喜欢。）

I know that with C# 3.0 or above I can use Automatic Properties. I like it even more :).

我的问题是关于一个（也许更老）代码，我可以看到这一点：

My question is about a (maybe older) code where I can see this:

   private int age;

   public int Age {

     get { return age; }
     set { age = value; }     
   }

为什么我需要私人领域的时代？什么？我真躲在这里

Why do I need the private field age? What I'm I really hiding here?

编辑：

我完全理解为吸气的需要，二传手。我提到我是从Java世界，并正在添加该做的一切的时候。

I completely understand the need for the getter and setter. I mentioned that I'm comming from Java world and doing this all the time.

我不明白，在C＃3.0或以上的自动属性是语法糖。但也许我的问题有一个简单的答案。难道这意味着（波纹管C＃3.0），酒店不持有任何价值。因此，它必须从其他字段中的值？

I do understand that Automatic Properties in C# 3.0 or above are syntatic sugar. But maybe my question has a simpler answer. Does it means that (bellow C# 3.0) the property doesn't hold any value. So it must get the value from some other field?

推荐答案

C＃的旧版本没有自动属性，所以你不得不声明变量的性质的，好像行动你的榜样。这些天来，同样的代码可以表示为：

Older versions of C# didn't have automatic properties, so you had to declare your variables that the properties acted upon like in your example. These days, the same code could be expressed as:

public int Age { get; set; }

我认为回答你的问题。但是，如果你问为什么不只是公众诠释年龄;而让程序员直接设置在球场上的价值？，则：

I think that answers your question. However, if you are asking "why not just have public int Age; and let programmers set the value on the field directly?", then:

首先要保持想到的是，属性访问被编译成方法。这意味着，它有不同的ABI只从读/写一个类的成员变量，即使它可能语法看起来是一样的，如果你有：

First thing to keep in mind is that property accessors are compiled into methods. This means that it has a different ABI from just reading/writing to a class member variable, even though it may syntactically look the same as if you had:

class Fu {
  public int Age;
}

那么，这是什么意思是，如果在某一点的道路，您需要添加一些通知年龄场发生了变化 - 如果你正在使用的属性，你可以轻松地添加此通知逻辑属性setter不打破ABI

So, what this means is that if, at some point down the road, you need to add some notification that the Age field has changed - if you are using properties, you can easily add this notification logic to the property setter without breaking ABI.

public int Age {
  get { return age; }
  set { age = value; NotifySomeOtherCode (); }
}

如果您与公共领域的开始，后来将其更改为一个属性将改变ABI这是坏的任何程序（县），可能取决于你的装配。所以，最好是具有属性开始。

If you start off with a public field, then later changing it to a property will change the ABI which is bad for any program(s) that may depend on your assembly. So it's better to start off with properties.

希望我做意义......

Hopefully I'm making sense...

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