Why doesn't C# support multiple inheritance?

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re: Why doesn't C# support multiple inheritance?

Phil — Mon, 08 Mar 2004 04:08:00 GMT

For me, MI is interesting when:
- you want to inherit the default behavior of an interface
- you want to have an object which can interact with two libraries.

If I could specify within an attribute the default implementaiton for an interface, that would be great.

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re: Why doesn't C# support multiple inheritance?

Shital Shah — Wed, 07 Apr 2004 19:56:00 GMT

From theoratical point of view MI is an nessecity. In many situations we need to make a decision whether to define an interface or an abstract class with same signatures. An interface and abstract class are exactly the samething except abstract class would allow some non-abstract members which can act as shared common code plus it can have protected overridable members. If MI is not supported then I have to really think whether to put my signatures in interface or an abstract class and decision would be based on limited knowledge whether client classes could have been already been derived from other class. So in nutshell, if there is no MI, my ability to share common code along with abstract members gets limited.

re: Why doesn't C# support multiple inheritance?

Felix — Thu, 13 May 2004 01:57:00 GMT

If I run into the problem of sharing common code as Shital described above, I use a mix of multiple interfaces and the Bridge Pattern. The class that needed to have multiple inheritance implements multiple Interfaces. Then, that same class will contain the Concrete Abstraction of the Bridge.

re: Why doesn't C# support multiple inheritance?

Kjell Holmgren — Fri, 14 May 2004 16:05:00 GMT

Personally, I would love mixins, as it would most elegantly address many of my issues with the implementation inheritance system of the CLR.

Also, I have the gut feeling that mixins would fit better into the philosophy of the .Net framework; in one swoop it would address the lack of multiple inheritance and the inability of doing template meta-programming ATL-style with the CLR generics.

Besides, I would love the AOP aspect [pun] of mixins; I imagine the mixin implementation would function better, smoother, and perform better than messing with Context bound objects and message sinks…

Since we are discussing single (implementation) inheritance versus multiple inheritance, what about single dispatch versus multiple dispatch? :-)

Why Multiple Inheritance was not implemented in .NET

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re: Why doesn't C# support multiple inheritance?

Balaji Birajdar — Thu, 08 Oct 2009 13:40:41 GMT

In object-oriented programming languages with multiple inheritance and knowledge organization, the diamond problem is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C. If a method in D calls a method defined in A (and does not override the method), and B and C have overridden that method differently, then from which class does it inherit: B, or C?

For example, in the context of GUI software development, a class Button may inherit from both classes Rectangle (for appearance) and Clickable (for functionality/input handling), and classes Rectangle and Clickable both inherit from the Object class. Now if the equals method is called for a Button object and there is no such method in the Button class but there is an overridden equals method in both Rectangle and Clickable, which method should be eventually called?

It is called the "diamond problem" because of the shape of the class inheritance diagram in this situation. In this article, class A is at the top, both B and C separately beneath it, and D joins the two together at the bottom to form a diamond shape.