DBNULL not Validate well

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Hi,

In my application i'm checking conditions with following way, but it seems not validating well(Always my catch block got exception).

C#

if (dtable.Rows[0]["VAT"] != System.DBNull.Value) //Exception here while it returns DBNULL
                       dreturns = Convert.ToDecimal(dtable.Rows[0]["VAT"]);
                   else
                       dreturns = 0;

Any help would be appreciated.

Catched Error is :

Error : System.NullReferenceException: Object reference not set to an instance of an object.

Posted 4-Mar-12 20:02pm

J.Karthick

Updated 27-Jun-18 0:03am

v2

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Comments

Sushil Mate 5-Mar-12 2:11am

Hope that table is not empty? can you put the value of that table?

J.Karthick 5-Mar-12 2:13am

Yes....Thats what i'm checking this condition.Whether its empty or not

Ed Nutting 5-Mar-12 2:28am

No he means does it actually have any rows in the table - if there are no rows then trying to get the value of VAT for row 0 isn't going to work and would throw the exception that you're getting. To test if the table is empty try doing: dtable.Rows.Count > 0 (I can't check this but it will be similar to this. It may be that Count is a method and so needs to be called as one.

Hope this helps,
Ed

J.Karthick 5-Mar-12 3:52am

I have pasted my actual solution. Please check it out.

Thanks for your comments

4 solutions

Solution 1

You need to check if the statement returned a row at all:

C#

dreturns = 0;
if (dtable.Rows.Count > 0)
{
    if (dtable.Rows[0]["VAT"] != System.DBNull.Value)
        dreturns = Convert.ToDecimal(dtable.Rows[0]["VAT"]);
}

Posted 4-Mar-12 20:29pm

Bernhard Hiller

Comments

ProEnggSoft 5-Mar-12 2:59am

This is the correct solution. Comment above by Ed Nutting also points to the same thing. My 5.

J.Karthick 5-Mar-12 3:49am

Nope....I don't accept this.

If my dtable is 'NULL' then how can i check row count ???

Even i tried this already.

Solution 3

C#

if (!DBNull.Value.Equals(dtable.Rows[0]"VAT"])                        
                      dreturns = Convert.ToDecimal(dtable.Rows[0]["VAT"]);
                   else
                       dreturns = 0;

Posted 4-Mar-12 23:19pm

Haneef Shaik

Comments

J.Karthick 5-Mar-12 5:32am

yes...its also an another method to do it.

Thanks

Solution 4

Try comparing the value of the column to the DBNull.Value value to filter and manage null values in whatever way you see fit.

C#

foreach(DataRow row in dtable.Rows)
{
    object value = row["VAT"];
    if (value == DBNull.Value)
        // do something
    else
        // do something else
}

Posted 27-Jun-18 0:04am

sambac8888

Comments

Richard Deeming 27-Jun-18 10:16am

SIX YEARS too late. The question already has a couple of very similar solutions - except yours changes the behaviour of the code.

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J.Karthick · Accepted Answer · 2012-03-04T21:51:00

Solution 2

C#

dreturns = 0;
if ( dtable != null && dtable.Rows.Count > 0 )
{
    if (dtable.Rows[0]["VAT"] != System.DBNull.Value)
        dreturns = Convert.ToDecimal(dtable.Rows[0]["VAT"]);
}

is this solution i get over.

Anyways thanks for CP members for their support.

Posted 4-Mar-12 21:51pm

J.Karthick