What do two question marks together mean in C#?

Question

Ran across this line of code:

FormsAuth = formsAuth ?? new FormsAuthenticationWrapper();

What do the two question marks mean, is it some ki

Answer 1

It's the null coalescing operator.

http://msdn.microsoft.com/en-us/library/ms173224.aspx

Yes, nearly impossible to search for unless you know what it's called! :-)

EDIT: And this is a cool feature from another question. You can chain them.

Hidden Features of C#?