Help with Generic LIst

[daimous]

hello dudes! i have a generic list and I add value to it using the code below

        public List<string> lstMainAlarm = new List<string>();
        lstMainAlarm.Add(Alarm_Id);

but i can't figure out how to check is X value exist I already use .Exist but i can't figure out how to use it. what is predicate? any inputs please..