یه نکته Linq

for (int i = 0; i < Math.Ceiling((double)arryIdToSearch.Count() / 2000); i++)
{
userVisitList.AddRange(_dx.UserAdvertisementVisits.Where(s => arryIdToSearch.Skip(i * 2000).Take(2000).Contains(s.Advertisement_Id) && s.User_Id == userId));
}