DBNull after read, need to cast

[patrick.sannes]

Hi,

I have a question. I have a stored procedure that can give a value
like a string or an int. But in some cases it can be DBNull. What is
the standard way to handle this?
- I can create a storedprocedure that always give the 0 value of the
type.
- Create an if statement around every assignment.

Maybe someone else have an idea?

Patrick

[patrick.sannes]

On 5 mrt, 17:12, patrick.san...@ gmail.com wrote:

Hi,

I have a question. I have a stored procedure that can give a value
like a string or an int. But in some cases it can be DBNull. What is
the standard way to handle this?
- I can create a storedprocedure that always give the 0 value of the
type.
- Create an if statement around every assignment.

Maybe someone else have an idea?

Patrick

At this moment I have this code
if (rdr["MatchBwDepotNr "].GetType() !=
typeof(System.D BNull) )
{
Input.BwplDepot Nr =
Convert.ToInt32 (rdr["MatchBwDepotNr "]); ;
}
And I think it is quite big if you have to do it for every record....
I hope there is a quicker way to do it.

[DeveloperX]

On 5 Mar, 16:18, patrick.san...@ gmail.com wrote:

On 5 mrt, 17:12, patrick.san...@ gmail.com wrote:

Hi,

I have a question. I have a stored procedure that can give a value
like a string or an int. But in some cases it can be DBNull. What is
the standard way to handle this?
- I can create a storedprocedure that always give the 0 value of the
type.
- Create an if statement around every assignment.

Maybe someone else have an idea?

Patrick

At this moment I have this code
if (rdr["MatchBwDepotNr "].GetType() !=
typeof(System.D BNull) )
{
Input.BwplDepot Nr =
Convert.ToInt32 (rdr["MatchBwDepotNr "]); ;
}
And I think it is quite big if you have to do it for every record....
I hope there is a quicker way to do it.

if(DBNull.Value == rdr["MatchBwDepotNr "])
{
//we are null
}

should do it.

And if you know the column ordinal rdr.IsDBNull(co lumn number) works
too, but who wants to work with ordinals.

framework 2 might allow rdr["MatchBwDepotNr "].IsDBNull, but I i don't
have it on this PC so I can't check.

[Jon Skeet [C# MVP]]

DeveloperX <nn*****@operam ail.comwrote:

And I think it is quite big if you have to do it for every record....
I hope there is a quicker way to do it.

if(DBNull.Value == rdr["MatchBwDepotNr "])

Or:

if (rdr["MatchBwDepotNr "] is DBNull)

which I think is the neatest version.

(Note that the whole constant==varia ble idiom isn't required in C#, as
only boolean expressions are valid for "if" statements. Even if I were
to use ==, I'd suggest reversing the operands from your code, to make
it easier to read.)

--
Jon Skeet - <sk***@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

[sherifffruitfly]

On Mar 5, 2:34 pm, Jon Skeet [C# MVP] <[e-mail] wrote:

Even if I were
to use ==, I'd suggest reversing the operands from your code, to make
it easier to read.)

You don't subscribe to the catch-inadvertent-assignment-typos-at-
compile-time methodology then, I take it?

cdj

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Jon Skeet [C# MVP] wrote:

DeveloperX <nn*****@operam ail.comwrote:

>>And I think it is quite big if you have to do it for every record....
I hope there is a quicker way to do it.

if(DBNull.Valu e == rdr["MatchBwDepotNr "])

Or:

if (rdr["MatchBwDepotNr "] is DBNull)

which I think is the neatest version.

if(rdr.IsDBNull (ColNoMatchBwDe potNr))

would be my preferred way if column number is an option.

Arne

[Jon Skeet [C# MVP]]

sherifffruitfly <sh************ *@gmail.comwrot e:

On Mar 5, 2:34 pm, Jon Skeet [C# MVP] <[e-mail] wrote:

Even if I were
to use ==, I'd suggest reversing the operands from your code, to make
it easier to read.)

You don't subscribe to the catch-inadvertent-assignment-typos-at-
compile-time methodology then, I take it?

Try reversing the operands - it won't compile. C# doesn't have the same
problem as C, because if (foo) will only compile if the type of "foo"
is boolean.

--
Jon Skeet - <sk***@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

[DeveloperX]

On 6 Mar, 07:13, Jon Skeet [C# MVP] <[e-mail] wrote:

sherifffruitfly <sherifffruit.. [e-mail] e:

On Mar 5, 2:34 pm, Jon Skeet [C# MVP] <[e-mail] wrote:

Even if I were
to use ==, I'd suggest reversing the operands from your code, to make
it easier to read.)

You don't subscribe to the catch-inadvertent-assignment-typos-at-
compile-time methodology then, I take it?

Try reversing the operands - it won't compile. C# doesn't have the same
problem as C, because if (foo) will only compile if the type of "foo"
is boolean.

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

It's force of habit and it does stop me doing if (b = true) :)

Google groups seems to be playing up, so this is the only post I can
read in this thread at the moment, apologies if I've missed something.

[Jon Skeet [C# MVP]]

On Mar 6, 1:15 pm, "DeveloperX " <nntp...@operam ail.comwrote:

It's force of habit and it does stop me doing if (b = true) :)

How often do you write that rather than if (b) anyway? I can't
remember the last time I did - and I don't think I've *ever*
accidentally written if (b=true).

To me, it feels obvious that

if (x==5)
is easier to read than
if (5==x)

- it's a more natural way of thinking about things. I would always
say, "Is your name Peter?" rather than "Is Peter your name?" for
instance.

Just because C/C++ is broken enough to make it worth bending
readability for safety doesn't mean it's worth preserving that habit
in saner languages :)

Google groups seems to be playing up, so this is the only post I can
read in this thread at the moment, apologies if I've missed something.

Nah, not a lot :)

Jon

[DeveloperX]

On 6 Mar, 13:50, "Jon Skeet [C# MVP]" <[e-mail] wrote:

On Mar 6, 1:15 pm, "DeveloperX " <nntp...@operam ail.comwrote:

It's force of habit and it does stop me doing if (b = true) :)

How often do you write that rather than if (b) anyway? I can't
remember the last time I did - and I don't think I've *ever*
accidentally written if (b=true).

To me, it feels obvious that

if (x==5)
is easier to read than
if (5==x)

- it's a more natural way of thinking about things. I would always
say, "Is your name Peter?" rather than "Is Peter your name?" for
instance.

Just because C/C++ is broken enough to make it worth bending
readability for safety doesn't mean it's worth preserving that habit
in saner languages :)

Google groups seems to be playing up, so this is the only post I can
read in this thread at the moment, apologies if I've missed something.

Nah, not a lot :)

Jon

Perfectly reasonable point, I would do if(b) too. Well I'll try and
break the habit, but it's been a long time, what's the betting the
first time I do I introduce a fatal bug :)