I thought I knew C#

I honestly thought I had a pretty fair grasp on C# for the last few years.

But apparently there are features that I haven’t known about.

The first one is covariance on arrays in C#

string[] strings = new[]{"Hello","Covariance"};

//assign the string array to an object array
object[] objects = strings;

objects[0] = "Hi"; //OK
objects[1] = 123; //runtime exception

I know that true covariance and contravariance will come in C# 4.

But I really didn’t know it was already implemented for arrays, I found this out maybe two months ago.

Also note the last line, we got dynamic type checks in C# , ewwww 😉

Another feature I didn’t know about is this:

this = new Foo();

Think I’m kidding with you?

Assignments to “this” ??

This is actually possible inside structs, which makes sense when you think about it, since you only overwrite the memory for the struct.

But I honestly didn’t know this was possible until I saw the Tuple struct in MEF a few days ago.

Maybe this is common knowledge, but if someone had told me that you could assign values to “this” in C# before I saw that, I would have slapped him.

//Roger