为何C#不使用多继承？(from stackoverflow)

       简单地说：是由于该语言的设计者决定不使用。

       基本上，.NET和Java的设计者不使用多继承（MI），是由于他们认为给语言加上多继承得到的好处较少，抵不上所以增长的复杂性。

      一、不一样的语言对于多继承如何工做实际上有不一样的指望。好比说，在冲突时基类如何合并或处理冗余。在CLR中实现多继承以前，咱们须要查看一下全部其余的语言，看看一些共通的概念，并在一种语言-中立的方式来表示它们。咱们还须要决定多继承是否应存在   于CLS，而这对于不想要这个概念的语言（好比说可能有VB.NET）。固然，这本是公共语言运行时的份内之事，然而咱们没有找到足够的时间为此来作。

      二、多继承真正合适的地方实际上不多。在不少状况下，多接口实现均可以作这个事。在其余状况下，你可使用封装和委托。假如咱们添加一个稍微不一样的构造器，如mixins，会更强大吗？

      三、多继承给实现增长了不少的复杂性。这个复杂性影响了类型转换，布局，字段访问，序列化，身份比较，可验证，反射，泛型以及可能还有不少别的地方。

 

      原文:

      The short answer is: because the language designers decided not to.

      Basically, it seemed that both the .NET and Java designers did not allow multiple inheritance because they reasoned that adding MI added too much complexity to the languages while providing too little benefit.

1. Different languages actually have different expectations for how MI works. For example, how conflicts are resolved and whether duplicate bases are merged or redundant. Before we can implement MI in the CLR, we have to do a survey of all the languages, figure out the common concepts, and decide how to express them in a language-neutral manner. We would also have to decide whether MI belongs in the CLS and what this would mean for languages that don't want this concept (presumably VB.NET, for example). Of course, that's the business we are in as a common language runtime, but we haven't got around to doing it for MI yet.

2. The number of places where MI is truly appropriate is actually quite small. In many cases, multiple interface inheritance can get the job done instead. In other cases, you may be able to use encapsulation and delegation. If we were to add a slightly different construct, like mixins, would that actually be more powerful?

3. Multiple implementation inheritance injects a lot of complexity into the implementation. This complexity impacts casting, layout, dispatch, field access, serialization, identity comparisons, verifiability, reflection, generics, and probably lots of other places.

 

引自：http://stackoverflow.com/questions/995255/why-is-multiple-inheritance-not-allowed-in-java-or-c