var test2NotInTest1 = test2.Where(t2 => test1.Count(t1 => t2.Contains(t1))==0);
Faster version as per Tim’s suggestion:
var test2NotInTest1 = test2.Where(t2 => !test1.Any(t1 => t2.Contains(t1)));
var test2NotInTest1 = test2.Where(t2 => test1.Count(t1 => t2.Contains(t1))==0);
Faster version as per Tim’s suggestion:
var test2NotInTest1 = test2.Where(t2 => !test1.Any(t1 => t2.Contains(t1)));