Comments on: C#: Using virtual leads to confusion?

By: Carlo

Carlo — Thu, 07 May 2009 19:42:11 +0000

I see where you're going with that. My take is that as long as there isn't lots of behaviour then the base class referencing subclasses isn't an issue.

By: Mark Brackett

Mark Brackett — Thu, 07 May 2009 16:35:47 +0000

I think I'd word this argument more along the lines of "making RedirectToErrorPage = true by default is bound to cause confusion when you inherit the same class for both errors and successes". Not anywhere as catchy, but highlights the real problem AFAIC.

In other words – why would a ResponseStatus (1) care whether your UI redirects to an error page, and (2) default to true?

By: Rob Scott

Rob Scott — Thu, 07 May 2009 14:36:18 +0000

I'm pretty sure that a better title might have been "Deriving from concrete class causes confusion". It's long been recognized that deriving from concrete classes is problematic. For a C++ version of the argument see Scott Meyers "More Effective C++", Item 33.

By: Mark Needham

Mark Needham — Thu, 07 May 2009 08:27:22 +0000

@Carlo yeh it's definitely still inheritance – that was supposed to be a more general comment about where the virtual key word might be useful.

I'm not sure, maybe it is. The idea was to only use the objects like:

ResponseStatus.UnrecoverableError or ResponseStatus.TransactionSuccessful so I'm not sure if it's quite so bad or not?

By: Carlo

Carlo — Thu, 07 May 2009 08:20:28 +0000

I can't see the composition behaviour above, it still is inheritance…

Isn't it also bad practice to let base classes know about their sub-classes i.e. The 2 static fields in the base class.

By: Reflective Perspective - Chris Alcock » The Morning Brew #342

Reflective Perspective - Chris Alcock » The Morning Brew #342 — Thu, 07 May 2009 07:38:55 +0000

[...] C#: Using virtual leads to confusion? – Mark Needham looks at some code that caused confusion due to its structure, and looks at a clearer alternative. [...]

By: DotNetShoutout

DotNetShoutout — Wed, 06 May 2009 18:14:18 +0000

C#: Using virtual leads to confusion? at Mark Needham…

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