VS 2003, false data concurrency error

  • Thread starter Thread starter John
  • Start date Start date
J

John

Hi

I have a vs 2003 winform data app. All the data access code has been
generated using the data adapter wizard and then pasted into the app. The
problem I have is that I am getting a data concurrency error on
mydataadapter.update() method. I know that there is no data concurrency
problem as I am the only user testing the app. Obviously the error is
misleading. What can I do from here to fix this problem?

Thanks

Regards
 
"I am the only user testing the app" is not a valid indication of what
constitutes concurrency nor will it prevent a concurrency error. In a
nutshell, "concurrency" at the time of update is a requirement that the
original dataource be the same as it was when the initial query was issued.
This can occur with 1-to-infinity users.

What might happen with a single user that causes a concurrency error? The
best example I can think of is where a user updates a row in a datagrid but
does not execute a re-query, then tries to update the same row in the
datagrid again. Well, will the data in the datasource now match the original
query? It most certainly will not, and thus this is why the
Microsoft-generated update logic includes an additional query.

The most reliable and easiest technique to ensure concurrency is to use a
primary key column and timestamp column to compare against for concurrency
and to ensure that those columns you are using to ensure concurrency do in
fact match the original data at the time of update. If not, find out why.
 
There isn't a second process I can see that is updating the db. I have also
checked that all field sin the backend access db have required=no and Allow
Zero Length=Yes.

Any ideas? Thanks.

Regards
 
John said:
Hi

I have a vs 2003 winform data app. All the data access code has been
generated using the data adapter wizard and then pasted into the app. The
problem I have is that I am getting a data concurrency error on
mydataadapter.update() method. I know that there is no data concurrency
problem as I am the only user testing the app. Obviously the error is
misleading. What can I do from here to fix this problem?

Thanks

Regards
Click to expand...

If you are using generated code to do the updates, then it probably looks
for a record with every field matching the original value of the field in
your recordset. Something like this:

update myTable Set field1 = @field1, field2 = @field2
where field1 = @field1_prev, field2 = @field2_prev

....where @field1_prev and @field2_prev are the original values held in the
dataset for those fields (see DataRowViewState, which is maintained for
each row in the dataset).

So if you are changing any of the original values in the database somehow,
it won't find the record, and it will throw a concurrency error.

Hope this helps.
Robin S.
 
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