I have implemented a custom task information dialog and using data from e.Task. Is it by design for the e.Task.Deadline to return #01/01/0001 12.00AM# even when the date from the datatable NULL?
Yes, because the data type of the Deadline property (and all other date/time properties for that matter) is System.DateTime, which is a value type and thus does not support null. DateTime.MinValue (1/1/0001) is the logical equivalent of null as it implies that the date has not been explicitly set.