No data exists for the row/column.

[zekeman]

In VB 6 I vaguely recall that there were special methods for database calls

for reading NULL values. With ADO.Net is that still the case?

 

[cjard]

erm...

You have the IsNull() command of a datarow that tests if the row is null
Adiitionally, you can query whether the row("column").Value = DBNull.Value

But you really should be using typed datasets if possible, and they expose a property for each column:

PersonDataRow.IsFirstNameNull
PersonDataRow.IsLastNameNull

...