Its clever, read the tooltip on the button :)

All great, but why IsSmiley returns int? Is... should answer true or false, and then you can just count where its true: smileys.Count(IsSmiley);

Regex is reinstantised with each evaluation, its not optimal.

I thought that it has to do something with "Reverse Polish notation", you can read about at http://polymathprogrammer.com/2007/10/22/reverse-polish-notation-with-cs/ but it actually would make i++ faster than ++i (as the idea is ot first place values on stack and than acts on them)

then googling around I have found https://stackoverflow.com/questions/3346450/what-is-the-difference-between-i-and-i and ended up with being more confused :)

there could be some ideas around this with older languages, but from c# compiler I would expect to sort it out on its own, but will try to investigate further