Ahri versus Kassadin?

Hi, I'm fairly new to LoL, and I mean that in the sense that I've only started consistently playing recently, I have watched people play before. (level 36, 11 champs, cant play ranked yet). I am a mid player, very good mid, I've found a way to beat just about every champ I've come across as Kassadin, even Zoe, whom I did have trouble with for a while (and can still prove trouble given how she plays and how good she is). But Ahri is the one champ that always beats me, in cs, makes me back when I dont want to, and just overall always outlanes me, even if she doesnt kill me.

I'm not entirely sure how to beat Ahri in lane (she ALWAYS picks into me, i'm never last pick ever). She can use her Q which gives me a moment to go in to get some cs, but then she auto's me, and her auto's do in fact hurt quite a bit and I end up having to use potions when I dont want to. I do generally dodge her charm pretty well (side from some moments), she just simply poses as a threat as she has range on me with high damage auto attack as well as the threat of being hit by her charm when she closes in when im trying to farm cs.

Ahri also happens to be a very popular pick, so its not a matchup im new to i've had to deal with an Ahri several times, and out of those times I maybe beat her only a few times and those were cases of A: She diving ME, KASSADIN, under my turret B: A good jungle consistently ganking for me (for some reason, that is RARE when im against ahri) or C: its simply a bad Ahri that is just scared of me for some reason and lets me farm cs.