handling dbnulls

[=?Utf-8?B?cm9kY2hhcg==?=]

hey all,

if (DataReader["ParentId"].ToString() != String.Empty)
{
oCategory.Paren tId = Convert.ToInt32 (DataReader["ParentId"]);
}

ParentId has some null values coming from my database. Is this the correct
way to handle the nulls for this field (or any field for that matter)?

When i debug, inside the immediate window i type:
?DataReader["ParentId"]
{ }

I'm not sure what the 2 braces mean so i added the ToString() and just
checked for " ".

One more thing, about the Convert.ToInt32 is this ok to use? Why isn't there
just a Convert.ToInteg er?

thanks,
rodchar

[Jon Skeet [C# MVP]]

Re: handling dbnulls

On Aug 8, 2:56 pm, rodchar <rodc...@discus sions.microsoft .comwrote:

hey all,
>
if (DataReader["ParentId"].ToString() != String.Empty)
{
oCategory.Paren tId = Convert.ToInt32 (DataReader["ParentId"]);
}
>
ParentId has some null values coming from my database. Is this the correct
way to handle the nulls for this field (or any field for that matter)?

It's not a terribly nice way of doing it. I'd use

if (!(DataReader["ParentId"] is DBNull))
{
....
}

One more thing, about the Convert.ToInt32 is this ok to use? Why isn't there
just a Convert.ToInteg er?

Because the .NET type name is ToInt32. "ToInteger" would be ambiguous
between Int16, Int32 and Int64 (aka short, int, long in C#).

Jon

[madhatter2647@gmail.com]

Re: handling dbnulls

if (DataReader["ParentId"] != System.DBNull.V alue)

is the correct syntax

the 'two braces' are the identifier for the column in the datareader.

there is no 'convert.tointe ger' function because there are many types
of integer representations in the framework. Int16, Int32, Int64 for
signed integers (ie negative and positive numbers) and UInt32, which
is an unsigned integer (only positive numbers)

[Mark Rae [MVP]]

Re: handling dbnulls

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1186582283 .887081.236250@ b79g2000hse.goo glegroups.com.. .

It's not a terribly nice way of doing it. I'd use
>
if (!(DataReader["ParentId"] is DBNull))
{
...
}

Is there any appreciable difference between the above and:

if (DataReader["ParentId"] != DBNull.Value)
{
....
}


--
Mark Rae
ASP.NET MVP

http://www.markrae.net

[Jon Skeet [C# MVP]]

Re: handling dbnulls

On Aug 8, 3:25 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

"Jon Skeet [C# MVP]" <sk...@pobox.co mwrote in messagenews:118 6582283.887081. 236250@b79g2000 hse.googlegroup s.com...
>

It's not a terribly nice way of doing it. I'd use

>

if (!(DataReader["ParentId"] is DBNull))
{
...
}

>
Is there any appreciable difference between the above and:
>
if (DataReader["ParentId"] != DBNull.Value)
{
...
>
}

Well, when testing in a "positive" way I find

if (DataReader["ParentId"] is DBNull)

more readable than

if (DataReader["ParentId"] == DBNull.Value)

and I was just trying to be consistent with that :)

Jon

[=?Utf-8?B?cm9kY2hhcg==?=]

RE: handling dbnulls

Thanks everyone for this wealth of knowledge. As always, I appreciate it.
Rod.

"rodchar" wrote:

hey all,
>
if (DataReader["ParentId"].ToString() != String.Empty)
{
oCategory.Paren tId = Convert.ToInt32 (DataReader["ParentId"]);
}
>
ParentId has some null values coming from my database. Is this the correct
way to handle the nulls for this field (or any field for that matter)?
>
When i debug, inside the immediate window i type:
?DataReader["ParentId"]
{ }
>
I'm not sure what the 2 braces mean so i added the ToString() and just
checked for " ".
>
One more thing, about the Convert.ToInt32 is this ok to use? Why isn't there
just a Convert.ToInteg er?
>
thanks,
rodchar

[Mark Rae [MVP]]

Re: handling dbnulls

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1186585323 .292596.17430@b 79g2000hse.goog legroups.com...

Well, when testing in a "positive" way I find
>
if (DataReader["ParentId"] is DBNull)
>
more readable than
>
if (DataReader["ParentId"] == DBNull.Value)
>
and I was just trying to be consistent with that :)

Fair enough.

BTW, this wasn't a criticism - I was just curious if "is" was more efficient
than "=="...


--
Mark Rae
ASP.NET MVP

http://www.markrae.net

[Jon Skeet [C# MVP]]

Re: handling dbnulls

Mark Rae [MVP] <mark@markNOSPA Mrae.netwrote:

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1186585323 .292596.17430@b 79g2000hse.goog legroups.com...
>

Well, when testing in a "positive" way I find

if (DataReader["ParentId"] is DBNull)

more readable than

if (DataReader["ParentId"] == DBNull.Value)

and I was just trying to be consistent with that :)

>
Fair enough.
>
BTW, this wasn't a criticism - I was just curious if "is" was more efficient
than "=="...

Sure - I wasn't taking it as a criticism.

I've no idea which is more performant to be honest - but I doubt that
it'll be the bottleneck in most code anyway, so I'd go with whatever's
most readable :)

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Ignacio Machin \( .NET/ C# MVP \)]

Re: handling dbnulls

Hi,

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1186585323 .292596.17430@b 79g2000hse.goog legroups.com...

On Aug 8, 3:25 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

>"Jon Skeet [C# MVP]" <sk...@pobox.co mwrote in
>messagenews:11 86582283.887081 .236250@b79g200 0hse.googlegrou ps.com...
>>

It's not a terribly nice way of doing it. I'd use

>>

if (!(DataReader["ParentId"] is DBNull))
{
...
}

>>
>Is there any appreciable difference between the above and:
>>
>if (DataReader["ParentId"] != DBNull.Value)
>{
>...
>>
>}

>
Well, when testing in a "positive" way I find
>
if (DataReader["ParentId"] is DBNull)
>
more readable than
>
if (DataReader["ParentId"] == DBNull.Value)
>
and I was just trying to be consistent with that :)

I like the latter more :)

It should be that I live in the tropics and you live in England :)