In .net, every instance of Object, or any type derived therefrom, includes a data structure which contains information about its type. "Real" value types in .net do not contain any such information. To allow data in value types to be manipulated by routines that expect to receive types derived from object, the system automatically defines for each value type a corresponding class type with the same members and fields. Boxing creates a new instances of this class type, copying the fields from a value type instance. Unboxing copies the fields from an instance of the class type to an instance of the value type. All of the class types which are created from value types are derived from the ironically named class ValueType (which, despite its name, is actually a reference type).

装箱并不是你真正使用的东西——它是运行时使用的东西，这样你就可以在必要时以同样的方式处理引用和值类型。例如，如果您使用ArrayList来保存整数列表，则整数将被装箱以适应ArrayList中的对象类型插槽。

现在使用泛型集合，这种情况几乎消失了。如果你创建一个List<int>，没有装箱完成- List<int>可以直接保存整数。

Boxing和Unboxing专门用于将值类型对象视为引用类型;将它们的实际值移动到托管堆并通过引用访问它们的值。

如果不进行装箱和拆箱，就无法通过引用传递值类型;这意味着您不能将值类型作为Object的实例传递。

在. net框架中，有两种类型——值类型和引用类型。这在面向对象语言中比较常见。

面向对象语言的一个重要特性是以类型不可知的方式处理实例的能力。这被称为多态性。由于我们希望利用多态性，但我们有两种不同的类型，因此必须有某种方法将它们组合在一起，以便以相同的方式处理其中一个或另一个。

现在，回到过去(Microsoft.NET 1.0)，还没有这种新奇的泛型喧闹。您不能编写一个方法，它只有一个参数，可以服务于值类型和引用类型。这违反了多态性。因此，采用装箱作为一种将值类型强制转换为对象的方法。

如果这是不可能的，那么框架中就会充斥着方法和类，它们的唯一目的就是接受其他类型。不仅如此，由于值类型并没有真正共享一个共同的类型祖先，因此必须为每种值类型(比特、字节、int16、int32等等)设置不同的方法重载。

拳击阻止了这种情况的发生。这就是英国人庆祝节礼日的原因。

In .net, every instance of Object, or any type derived therefrom, includes a data structure which contains information about its type. "Real" value types in .net do not contain any such information. To allow data in value types to be manipulated by routines that expect to receive types derived from object, the system automatically defines for each value type a corresponding class type with the same members and fields. Boxing creates a new instances of this class type, copying the fields from a value type instance. Unboxing copies the fields from an instance of the class type to an instance of the value type. All of the class types which are created from value types are derived from the ironically named class ValueType (which, despite its name, is actually a reference type).

一般来说，您通常会希望避免对值类型进行装箱。

然而，在极少数情况下，这是有用的。例如，如果您需要以1.1框架为目标，那么您将无法访问泛型集合。在. net 1.1中使用任何集合都需要将您的值类型视为系统。对象，该对象导致装箱/解装箱。

There are still cases for this to be useful in .NET 2.0+. Any time you want to take advantage of the fact that all types, including value types, can be treated as an object directly, you may need to use boxing/unboxing. This can be handy at times, since it allows you to save any type in a collection (by using object instead of T in a generic collection), but in general, it is better to avoid this, as you're losing type safety. The one case where boxing frequently occurs, though, is when you're using Reflection - many of the calls in reflection will require boxing/unboxing when working with value types, since the type is not known in advance.