Retrieving a byte array from an access database

  • Thread starter Thread starter Nak
  • Start date Start date
N

Nak

Hi there,

I'm sure this is pretty easy but I seem to be having problems, I have a
database that contains some binary data in some of the fields. As a test a
made this 2 bytes long with lets say "11" as it's contents (ASCII "1" &
"1"). Now when it comes to retrieving the data I am using this line of code

Call pDBRReader.GetBytes(5, 0, mybytearray, 0, Integer.MaxValue)

"pDBRReader is an OleDbDataReader"
"5 is the column in which the data resides"

I am not getting any exceptions thrown and the return value from this
line is 2, yet mybytearray is still Nothing, any ideas?? Cheers in
advance!!!!!

Nick.
 
Hi Nick,

First of all, I would like to confirm my understanding of your issue. From
your description, I understand that the buffer is still nothing when you
have called GetBytes. If there is any misunderstanding, please feel free to
let me know.

Based on your description, I think you didn't set the buffer mybytearray to
a valid object reference. We have to initialize it first before calling
GetBytes. Here is an example:

mybytearray = new Byte[Integer.MaxValue];
pDBRReader.GetBytes(5, 0, mybytearray, 0, Integer.MaxValue)

Based on the MSDN document, if you pass a buffer that is a null reference
(Nothing in Visual Basic), GetBytes returns the length of the field in
bytes without throwing any exception.

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."
 
Hi Kevin,

Thanks for the help, as you rightly suggested, I was passing a null
reference to the function thinking it would resize the array as necessary.
Cheers!

Nick.
 
Hi Kevin,

Unfortunately even after trying as you have suggested I am still being
given a null reference back. I have tried a few variations of initialising
the byte array first of all, i.e. via Redim and New keywords but still no
luck when I try to access the returned data. Any ideas?

Nick.

Nak said:
Hi Kevin,

Thanks for the help, as you rightly suggested, I was passing a null
reference to the function thinking it would resize the array as necessary.
Cheers!

Nick.

Kevin Yu said:
Hi Nick,

First of all, I would like to confirm my understanding of your issue.
From
your description, I understand that the buffer is still nothing when you
have called GetBytes. If there is any misunderstanding, please feel free
to
let me know.

Based on your description, I think you didn't set the buffer mybytearray
to
a valid object reference. We have to initialize it first before calling
GetBytes. Here is an example:

mybytearray = new Byte[Integer.MaxValue];
pDBRReader.GetBytes(5, 0, mybytearray, 0, Integer.MaxValue)

Based on the MSDN document, if you pass a buffer that is a null reference
(Nothing in Visual Basic), GetBytes returns the length of the field in
bytes without throwing any exception.

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."
Click to expand...
Click to expand...
 
Hi again....

I've sussed it now, the array needs to be initialised at the *correct*
length before passing it to the routine. Pants!

Nick.

Nak said:
Hi Kevin,

Thanks for the help, as you rightly suggested, I was passing a null
reference to the function thinking it would resize the array as necessary.
Cheers!

Nick.

Kevin Yu said:
Hi Nick,

First of all, I would like to confirm my understanding of your issue.
From
your description, I understand that the buffer is still nothing when you
have called GetBytes. If there is any misunderstanding, please feel free
to
let me know.

Based on your description, I think you didn't set the buffer mybytearray
to
a valid object reference. We have to initialize it first before calling
GetBytes. Here is an example:

mybytearray = new Byte[Integer.MaxValue];
pDBRReader.GetBytes(5, 0, mybytearray, 0, Integer.MaxValue)

Based on the MSDN document, if you pass a buffer that is a null reference
(Nothing in Visual Basic), GetBytes returns the length of the field in
bytes without throwing any exception.

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."
Click to expand...
Click to expand...
 
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