.net - Understanding Covariance and Contravariance in C# 4.0

Question

I watched a video about it on Channel 9 but I didn't really understand it much.

Can someone please give me a simple example about these that's easy to understand? After that maybe how it would be used in practice?

Answer 1

You may want to look at this blog, he does a fantastic job of explaining it, but I think it will take more examples to clear it up for people, as this gets into a very hard-to-understand area, but, the quote below from the article sums it up well.

http://hestia.typepad.com/flatlander/2008/12/c-covariance-and-contravariance-by-example.html

"covariance and contravariance" means that you can now pass inexact generic types when it's safe to do so, just as you can pass inexact argument types when it's safe to do so.