(This answer has been rewritten 2013-05-13, read the discussion in the bottom of the comments) LSP is about following the contract of the base class. You can for instance not throw new exceptions in the sub classes as the one using the base class would not expect that. Same goes for if the base class … Read more
Because an array allows fast access by index, and IList/IList<T> are the only collection interfaces that support this. So perhaps your real question is “Why is there no interface for constant collections with indexers?” And to that I have no answer. There are no readonly interfaces for collections either. And I’m missing those even more … Read more
A great example illustrating LSP (given by Uncle Bob in a podcast I heard recently) was how sometimes something that sounds right in natural language doesn’t quite work in code. In mathematics, a Square is a Rectangle. Indeed it is a specialization of a rectangle. The “is a” makes you want to model this with … Read more