NULLS HANDLING IN C#

[Raul M. Colon]

Hi! Im developing a web application that reads from a database and populate a
form with a DataReader. When the reader reach a null value in the database,
the application throws an exception. In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Thanks!!!

Raul

[MuZZy]

Raul M. Colon wrote:

Hi! Im developing a web application that reads from a database and populate a
form with a DataReader. When the reader reach a null value in the database,
the application throws an exception. In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Thanks!!!

Raul

Why wouldn't you just check if returned value is null?
while (reader.Read())
{
if (reader.getValue(<column_number>) == null)
{<...do whatever...>}
}

Good luck,
Andrey aka Muzzy

[Anders Norås [MCAD]]

> ... In VB I used the IsDBNull function to

catch and process the null values.

Is there a similar function in C#???

Yes. Just compare the value to DBNull.Value to check if it is a null value.

Anders Norås
http://dotnetjunkies.com/weblog/anoras/

[MuZZy]

Anders Norås [MCAD] wrote:

... In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Yes. Just compare the value to DBNull.Value to check if it is a null value.

Anders Norås
http://dotnetjunkies.com/weblog/anoras/

Do you need to check against DBNull.Value if you use DataReader?
If a value is null, then DataReader.GetValue() returns just null...

Am i missing something here?

Thank you,
Andrey

[Tom Porterfield]

On Mon, 27 Dec 2004 17:06:25 -0500, MuZZy wrote:

Why wouldn't you just check if returned value is null?

while (reader.Read())
{
if (reader.getValue(<column_number>) == null)
{<...do whatever...>}
}

Because null != DBNull. You can either compare to DBNull.Value, or more
familiar to VB programmers maybe would be to use Convert.IsDBNull.
--
Tom Porterfield

[Raul M. Colon]

I was the one missing the point. Thanks for your replies, the combination of

if(reader.GetValue == DBNull.Value)
{ .....
}

worked fine. Thanks!!!
"MuZZy" wrote:

Anders Norås [MCAD] wrote:

... In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Yes. Just compare the value to DBNull.Value to check if it is a null value.

Anders Norås
http://dotnetjunkies.com/weblog/anoras/

Do you need to check against DBNull.Value if you use DataReader?
If a value is null, then DataReader.GetValue() returns just null...

Am i missing something here?

Thank you,
Andrey

[Cor Ligthert]

Tom,

Because null != DBNull. You can either compare to DBNull.Value, or more
familiar to VB programmers maybe would be to use Convert.IsDBNull.

In my opinion the same as C# however using than the IS operator (when you
are talking about VBNet).

Cor

[Jon Skeet [C# MVP]]

Raul M. Colon <Ra********@discussions.microsoft.com> wrote:

Hi! Im developing a web application that reads from a database and populate a
form with a DataReader. When the reader reach a null value in the database,
the application throws an exception. In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Another possibility no-one has mentioned is not to fetch the value, but
to use the IsDBNull method on the DataReader, specifying the
appropriate column.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Bob Grommes]

null is C# syntax for determining if an instance variable is not initialized
or not currently pointing to an actual object. That is not the same thing
as database NULLness, which has a completely different meaning -- it
signifies an unknown value, not an undefined object reference.

--Bob

"MuZZy" <le*******@yahoo.com> wrote in message
news:tq********************@rcn.net...

Raul M. Colon wrote:

Hi! Im developing a web application that reads from a database and
populate a form with a DataReader. When the reader reach a null value in
the database, the application throws an exception. In VB I used the
IsDBNull function to catch and process the null values.

Is there a similar function in C#???

Thanks!!!

Raul

Why wouldn't you just check if returned value is null?
while (reader.Read())
{
if (reader.getValue(<column_number>) == null)
{<...do whatever...>}
}

Good luck,
Andrey aka Muzzy

[Hugo Wetterberg]

On Mon, 27 Dec 2004 13:55:03 -0800, Raul M. Colon wrote:

Hi! Im developing a web application that reads from a database and populate a
form with a DataReader. When the reader reach a null value in the database,
the application throws an exception. In VB I used the IsDBNull function to
catch and process the null values.

Is there a similar function in C#???

Thanks!!!

Raul

if(reader["fieldName"] is DbNull)
{
//Do something
}

/Hugo