System.Data.StrongTypingException

to fix this exception in strong-type dataset use method IsNull method before reading value to avoid this exception.

in C# it will be like :
if (!logins[0].Isincorrect_attempt_dateNull())
{
 incor_pass_hours_ago = DateTime.Now.Subtract((DateTime)logins[0].incorrect_attempt_date).TotalHours;
}