请帮我理解类型对象的一些c＃basic（ref与值，拳击） [英] Please help me to understand some c# basic's on type object (ref vs. value, boxing)

问题描述

我正在尝试理解c＃中的一些基础知识。我确信我理解了引用类型和值类型的基础知识。但在MSDN中阅读后，我变得越来越困惑（以下两个链接只能解释我为什么得出结论，例如骨头）：



http://msdn.microsoft.com/de-de/library/490f96s2.aspx [ ^ ]

对象类型是Object的别名

- >我希望理解正确

类型对象是参考类型的_build_

- >对象是引用类型





http://msdn.microsoft.com/de-de/library/9kkx3h3c.aspx [ ^ ]

...在C＃的统一类型系统中，所有类型，预定义的和用户定义的，引用类型和值类型，直接或间接地从Object继承。您可以将任何类型的值分配给object类型的变量。当一个值类型的变量转换为object时，它被称为盒装。

- >混淆：引用类型和值类型，直接或间接地从Object继承。



示例

从上面我总结说，对象可以是像两者一样并尝试（也许是天真）跟随，_assuming_我使用对象是一种引用类型：

I'm trying to understand some basics in c#. I'm convinced that I understand the basics of reference types and value types. But after reading in MSDN I'm becoming more and more confused (the following two links do only explain why I came to my conclusion, Example is the bone):

http://msdn.microsoft.com/de-de/library/490f96s2.aspx[^]
The object type is an alias for Object
--> That I hopefully understand right
Type object is a _build in reference type_
--> object is a reference type


http://msdn.microsoft.com/de-de/library/9kkx3h3c.aspx[^]
...In the unified type system of C#, all types, predefined and user-defined, reference types and value types, inherit directly or indirectly from Object. You can assign values of any type to variables of type object. When a variable of a value type is converted to object, it is said to be boxed.
--> confusion: reference types and value types, inherit directly or indirectly from Object.

Example
From the above I concluded that object can be "something like both" and tried the (maybe naiv) following, _assuming_ I'm using object is a reference type:

int int1 = 1;
object boxint1 = int1;   // here also tried boxint1= new object()...same result
object boxint2 = boxint1;

boxint1 = (int)boxint1 + 1;
boxint2 = (int)boxint2 + 1;
              
// At this point I expected that
//   boxint1 is equal to 2
//   boxint2 is equal to 3
// but both are equal to 2 

例如 http://msdn.microsoft.com/de-de/library/yz2be5wk.aspx [ ^ ]包含一个很好的图形内存情况是盒装类型



有人可以帮助我解决这个令人困惑的问题。解释一下我的理解/误解是完全错的？



非常感谢advacne。

Bruno

e.g. http://msdn.microsoft.com/de-de/library/yz2be5wk.aspx[^]contains a nice graphic how memory situation is for boxed types

Can somebody help me out of this confusing resp. explain me what I'm understanding/misinterpretingthat completely wrong?

Thank you very much in advacne.
Bruno

推荐答案

这可能看起来令人困惑，但实际上相当简单。 :)



首先考虑引用类型：

This might look confusing, but it's actually fairly simple. :)

Start by thinking about reference types:

Person a = new Person("Bruno");
Person b = a;

此时， a 和 b 指向同一个对象。

At this point, both a and b are pointing to the same object.

a = new Person("Richard");

现在 a 指向另一个对象。如果 b 也改为指向新对象，那将是非常令人惊讶的！





对于普通值类型，适用相同的语义：

Now a is pointing to a different object. It would be quite surprising if b was also changed to point to the new object!


With normal value types, the same semantics apply:

int a = 1;
int b = a;
a = 2;

如果在运行此代码后<$ c，那将是令人惊讶的$ c> b 已更改为 2 。





使用盒装值类型，适用相同的语义。装箱值类型有效地创建了一个新的盒子来存储盒装值的副本。如果在同一个变量中存储一个新的盒装值，它不会自动影响指向同一个盒子的其他变量。

It would be surprising if, after running this code, b had been changed to 2.


With boxed value types, the same semantics apply. Boxing a value type effectively creates a new "box" to store a copy of the value being boxed. If you store a new boxed value in the same variable, it doesn't automatically affect other variables pointing to the same box.

int int1 = 1;
object boxint1 = int1;       // Imagine: object boxint1 = new BoxedInteger(int1);
object boxint2 = boxint1;    // Now boxint1 and boxint2 point to the same box.

boxint1 = (int)boxint1 + 1;  // Imagine: boxint1 = new BoxedInteger((int)boxint1 + 1);
                             // Would you expect boxint2 to be changed here?

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