How to check if a Datatable is Null or Nothing

Question

How can I check if a DataTable has never been set, meaning it will be Null or Nothing? I don't mean an empty DataTable.

For example:

Dim dt As DataTable = TryCast(Session("dt"), DataTable)

If dt.Rows.Count <> 0 Then
    'Do something !
End If

If Session("dt")has never been set or is lost in memory for some reason, dt.Rows.Count <> 0 will throw this exception:

Object reference not set to an instance of an object.

For anyone else finding this and wants to know more check out the answers at [What is a NullReferenceException, and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Bugs, Mar 24 '17 at 08:54

score 19 · Accepted Answer · answered Apr 26 '12 at 10:25

19

Preferred:

If dt Is Nothing Then ...

or (VB6 like)

If IsNothing(dt) Then ...

answered Apr 26 '12 at 10:25

Tim Schmelter

hehe ... of course .. why was I being so silly just now ... Thanks .. :D – Laurence Apr 26 '12 at 10:28
5

@LaurenceNyein your sillyness proved helpful to me :) – C Sharper Oct 22 '13 at 06:57

score 0 · Answer 2 · answered Aug 26 '20 at 17:15

0

dt2 = datatable If dt2.Rows.Count > 0

answered Aug 26 '20 at 17:15

Estus

score -1 · Answer 3 · answered Mar 24 '17 at 08:37

-1

If the value datatype is varbinary(MAX), use

if dt.rows(0).item(2) Is DBNull.Value then...

answered Mar 24 '17 at 08:37

ain

1

Please re-read the question. It explicitly asks to check when a `DataTable` has not been set. That means your code will fail. – Bugs Mar 24 '17 at 08:47

3 Answers3