we keep in mind:
Assign Activity:
dtFiltered =
(From d in YourDataTableVar.asEnumerable
Let dp = DateTime.ParseExact(row("Last Logon").ToString(), "M/d/yyyy", System.Gobalization.CultureInfo.InvariantCulture)
Where dp.Date < DateTime.Now.AddDays(-90).Date
Select r =d).CopyToDataTable
As mentioned above within the FirstAid we check the DataTable and align the DateTime parsing accordingly
Handling empty results:
Feel free to adapt the LINQ e.g. by handling empty row values / non parseable values etc