Best Practice when trying to Load object from Data Layer when it doesn't find it

[TS]

If I was to have my biz layer ask the data layer to load a particular object
based on key field info i pass to it, and it cannot create the object
becaues it isnt' in the Db, should the data layer pass back an exception or
a null reference?

if an exception, i would imagine i should catch this and display a message
to the user?

thanks

[Tom Porterfield]

TS wrote:

If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?

if an exception, i would imagine i should catch this and display a message
to the user?

I would prefer some non-exception indicator that the record was not found.
If you want to return a null object, that would work. Don't forget to check
for null as you will get a null reference exception if you try to access the
object without checking for a null object reference first.

You might also consider using some other indicator such as a status code or
bool value that indicates whether or not the object was successfully created
from the DB.
--
Tom Porterfield

[sloan]

Exceptions should be "Exceptiona l"

Thus, if this is something you except to happen, then return a null.


"Tom Porterfield" <tp******@mvps. orgwrote in message
news:ek******** ******@TK2MSFTN GP03.phx.gbl...

TS wrote:

If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?

if an exception, i would imagine i should catch this and display a

message

to the user?

I would prefer some non-exception indicator that the record was not found.
If you want to return a null object, that would work. Don't forget to

check

for null as you will get a null reference exception if you try to access

the

object without checking for a null object reference first.

You might also consider using some other indicator such as a status code

or

bool value that indicates whether or not the object was successfully

created

from the DB.
--
Tom Porterfield

[Peter Bromberg [C# MVP]]

An exceptional comment from an exceptional guy.

:-)

--
Co-founder, Eggheadcafe.com developer portal:
http://www.eggheadcafe.com
UnBlog:
http://petesbloggerama.blogspot.com


"sloan" wrote:

>
Exceptions should be "Exceptiona l"

Thus, if this is something you except to happen, then return a null.


"Tom Porterfield" <tp******@mvps. orgwrote in message
news:ek******** ******@TK2MSFTN GP03.phx.gbl...

TS wrote:

If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?
>
if an exception, i would imagine i should catch this and display a

message

to the user?

I would prefer some non-exception indicator that the record was not found.
If you want to return a null object, that would work. Don't forget to

check

for null as you will get a null reference exception if you try to access

the

object without checking for a null object reference first.

You might also consider using some other indicator such as a status code

or

bool value that indicates whether or not the object was successfully

created

from the DB.
--
Tom Porterfield

[PS]

"TS" <ma**********@n ospam.nospamwro te in message
news:uA******** ******@TK2MSFTN GP02.phx.gbl...

If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?

I can think of a few different approaches to this.

1) null reference - you check that the object == null and handle accordingly
2) throw an exception - you catch the exception and handle accordingly
3) return a Null Object - you encapsulate the behavior of what to do when
the ID was not found into the object itself.
4) return a default object - you use another object as the default object
when the ID was not found
5) create an object with default values - you create an object with default
values and return this

What is the reason that the ID was not found in the database? Is this
something critical or something that is expected and you want to handle this
gracefully? If it is expected then do not throw an exception.

PS

For example

>
if an exception, i would imagine i should catch this and display a message
to the user?

[Rad]

On Mon, 13 Nov 2006 14:39:43 -0600, "TS" <ma**********@n ospam.nospam>
wrote:

>If I was to have my biz layer ask the data layer to load a particular object
based on key field info i pass to it, and it cannot create the object
becaues it isnt' in the Db, should the data layer pass back an exception or
a null reference?

if an exception, i would imagine i should catch this and display a message
to the user?

thanks

I guess it would depend on your application design. If NOT finding a
record with a given primary key is part of the application design i.e.
is part of the functionality then perhaps a null would suffice.

Personally I would throw an exception and handle that in the UI

[Kevin Yu [MSFT]]

Hi TS,

In my opinion, if you're returning some status code, it will be better if
you can have some status code for database not found. If you return the
object directly to the biz layer, I would suggest you throw an exception,
which makes difference to the certain data is not found.

If anything is unclear, please feel free to let me know.

Kevin Yu
Microsoft Online Community Support

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[TS]

this is something that happens infrequently in production system
"PS" <ec***********@ hotmail.comwrot e in message
news:uX******** ******@TK2MSFTN GP03.phx.gbl...

>
"TS" <ma**********@n ospam.nospamwro te in message
news:uA******** ******@TK2MSFTN GP02.phx.gbl...

>If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?

I can think of a few different approaches to this.

1) null reference - you check that the object == null and handle
accordingly
2) throw an exception - you catch the exception and handle accordingly
3) return a Null Object - you encapsulate the behavior of what to do when
the ID was not found into the object itself.
4) return a default object - you use another object as the default object
when the ID was not found
5) create an object with default values - you create an object with
default values and return this

What is the reason that the ID was not found in the database? Is this
something critical or something that is expected and you want to handle
this gracefully? If it is expected then do not throw an exception.

PS

For example

>>
if an exception, i would imagine i should catch this and display a
message to the user?

[Tom Porterfield]

TS wrote:

this is something that happens infrequently in production system

But that doesn't answer the important question. Is it truly unexpected, or
exceptional, behavior when the record isn't found. If it's not then you
shouldn't throw an exception. If it is, then that designed has more merit.
--
Tom Porterfield

[PS]

"TS" <ma**********@n ospam.nospamwro te in message
news:uT******** ******@TK2MSFTN GP02.phx.gbl...

this is something that happens infrequently in production system

And how does it happen? I mean how is it that the application manages to
know a key that does NOT exist in the database? Where does it get the keys
from?

>

"PS" <ec***********@ hotmail.comwrot e in message
news:uX******** ******@TK2MSFTN GP03.phx.gbl...

>>
"TS" <ma**********@n ospam.nospamwro te in message
news:uA******* *******@TK2MSFT NGP02.phx.gbl.. .

>>If I was to have my biz layer ask the data layer to load a particular
object based on key field info i pass to it, and it cannot create the
object becaues it isnt' in the Db, should the data layer pass back an
exception or a null reference?

I can think of a few different approaches to this.

1) null reference - you check that the object == null and handle
accordingly
2) throw an exception - you catch the exception and handle accordingly
3) return a Null Object - you encapsulate the behavior of what to do when
the ID was not found into the object itself.
4) return a default object - you use another object as the default object
when the ID was not found
5) create an object with default values - you create an object with
default values and return this

What is the reason that the ID was not found in the database? Is this
something critical or something that is expected and you want to handle
this gracefully? If it is expected then do not throw an exception.

PS

For example

>>>
if an exception, i would imagine i should catch this and display a
message to the user?