@JeremyECrawford eldritch blast + assassinate?
— Josh (@SirJosh94) May 31, 2016
The Assassinate feature works with attack rolls of any sort, including the attack roll in eldritch blast. #DnD https://t.co/Xddoh7TYuQ
— Jeremy Crawford (@JeremyECrawford) June 4, 2016
Assassinate pg 97 : grants advantage on attack rolls and grants a critical against surprised opponents.
Separately pg. 96 : Sneak attack requires Advantage (or ally within 5′) but also a ranged weapon or finesse weapon.
So you can use assassinate but you won’t get sneak attack with eldritch blast RAW. but a dm may allow it. ( rule of cool)