Is it possible to be friends with an ex?

I think you can only be friends with your ex if
A. You are both dating other people now
B. You were friends before you dated
C. The break-up was mutual
D. The break-up was classy (i.e. NOT being texted by the Bastard from Spain, which meant that you had to pay £7 to be dumped).

But if the guy dumped you brutally, or if you still have a little crush on him then DON'T TRY TO BE FRIENDS.
It sounds harsh and I may stand corrected but from my experience you cannot be friends with an ex because you may still feel resentful or, like me, you may still have a crush.
Basically over the last couple of days I fell down the Slippery Slope where I started to like Curly Haired Guy (the guy who kissed me and stringed me along and now he is dating a 10-yr-old hoe) after he said I deserve a lot more than how I am treated by guys and that I should wait for someone to treat me how I deserve and should give up on manwhores because I am too good for them.
Swoon.
BUT I HAVE DECIDED TO STOP THIS MADNESS. It is madness. He cannot just...be nice to me. He has to be mean and then I can slag him off to all my friends and loathe him with every fibre of my being. But, no. He has to be nice and confuse the fuck out of me.
I saw CHG again yesterday when he was at a party but he was so sad - his girlfriend and him are having problems or something. Look, I'm sure he loves his girlfriend and I am NOT Sloppy Seconds and I am also NOT a doormat so I cannot be friends with CHG.
But of course I am the Mayor of Numptyville. So I have been texting him. And now he has stopped replying. Just like Knight did. I am so sick of guys - Manwhores and Knobheads to be precise - who have fucked up my ability to trust people. I am so used to being treated like shit now that I have lost all confidence in romance, chivalry and all guys. I miss being the naive Grammar Gal, but now I am slightly more cynical.
Keep you posted,
Grammar Gal xxx