What should I use to compare DBNull ? Using DBNull.Value or ToString().IsNullOrEmpty()

Question

I can check for a DBnull on a data row using any of the methods.

Either by using

if(dr[0][0]==DBNull.Value)
//do somethin

or by doing

if(dr[0][0].ToString().IsNullOrEmpty())
//do something

In Both Cases I will be getting same result.

But Which one is conecptually right approach. Which was will use less resources

`.ToString().IsNullOrEmpty()`? Does a data **row** have 2 indices, `dr[0][0]`? And what if `dr[0][0]` is null, you can't call `.ToString()`. It is usually best to provide working code to get better answers. — Kobi, Aug 03 '10 at 06:10
@Kobi: My mistake you are right I meant to say DataTable if taking two indexers — Shantanu Gupta, Aug 03 '10 at 06:15
for the second case, if the value in that column is null you'll be getting an error — devnull, Aug 03 '10 at 06:21

score 24 · Accepted Answer · answered Aug 03 '10 at 06:10

24

The first way is somewhat correct. However, more accepted way is:

if ( dr[0][0] is DBNull )

And the second way is definitely incorrect. If you use the second way, you will get true in two cases:

answered Aug 03 '10 at 06:10

Fyodor Soikin

Rob · Answer 2 · 2010-08-03T06:29:00.313

9

Conceptually the comparison to DBNull.Value is the correct one.

You can also use :

if (Convert.IsDBNull(dr[0]))
{
}

You could also use, which I'm not a fan of, purely because it's a type comparison rather than a value comparison:

if (dr[0] is DBNull)
{
}

edited Aug 03 '10 at 06:29

answered Aug 03 '10 at 06:10

Rob

score 1 · Answer 3 · answered Aug 04 '10 at 10:07

1

Is always use :

dr[0].IsNull(0)

Assuming that the creators of this function know the best way/most efficient way of comparing..

answered Aug 04 '10 at 10:07

Julian de Wit

score 0 · Answer 4 · answered Jan 05 '17 at 19:09

The simplest way

if (dr[0][0] == DBNull.Value)
//do somethin

is perfectly valid and readable.

Even though == compares references, it works here because DBNUll.Value is the only instance of DBNull class - so all DBNull values are actually this exact reference.

4 Answers4