在未装箱的情况下,值类型不继承任何类型,装箱的情况下值类型才会继承ValueType或者Enum,并实现其它接口
[原文:In their unboxed form value types do not inherit from any type. Boxed value types shall inherit directly from System.ValueType unless they are enumerations, in which case, they shall inherit from System.Enum. Boxed value types shall be sealed.
摘自:Common Language Infrastructure(CLI) Partition I: Concepts and Architecture Final Draft, Apr 2005 第42页]