Thank you Tomas Petricek for explaining "The theory behind covariance and contravariance in C# 4"

Awesome: through this twitter notification ...

... I read the article written by Thomas Petricek on C# interface contra- and covariance. To be honest, I only learnt about this feature because ReSharper suggested me to make some of my interfaces either contra- or covariant. I read the spec what it meant, but didn't fully grasp it. 

Now at least, I've got a bit of idea and will take it from here. Really interesting stuff made easy to understand. Check it out here: http://tomasp.net/blog/variance-explained.aspx/