Annulment of marriage for concealing past affair

Hi, My name is Rahul sharma and got married this year. My wife had an affair/sexual relation with her boyfriend before marriage and had not disclosed to me before marriage. she has continued affair/adultery after marriage with her boy friend. I have evidence that wife has not disclosed about her past sexual relationship before marriage to me. If she has disclosed to me about her affair/sexual relation about this prior to marriage, i would have never agreed for marriage. Does this come under "constent to marriage was based on fraud" as she has concealed about her past sexual affair? 1. Can i file for annulment of marriage as in this case? 2. if we have good evidences, How long will annulment in general take? Thanks, Rahul