DataAdapter.Upd ate() and DataTable.GetCh anges() side effect.

[George]

Got a question about the side effect of DataAdapter.Upd ate() and
DataTable.GetCh anges().

Say I set up a DataTable and a DataAdapter in a class. Delete (Not remove)
a row in the data table and call the following method.

public void JobListDataTabl eFromAccessComm itChange()
{
System.Data.Dat aTable oChangeDataTabl e;

try
{
if (this.jobListDa taTable.HasErro rs)
{
throw (new
System.Applicat ionException(Er rDatabaseUpdate ));
}

oChangeDataTabl e = this.jobListDat aTable.GetChang es();
if (oChangeDataTab le != null)
{
this.JobListDat aAdapter.Update (oChangeDataTab le);

foreach (System.Data.Da taRow oDataRow in
oChangeDataTabl e.Rows)
{
if (oDataRow[JobDataGridView ColumnId] ==
System.DBNull.V alue)
{
this.jobListDat aTable.Clear();

this.jobListDat aAdapter.Fill(t his.jobListData Table);
break;
}
}

if (this.jobListDa taTable.HasErro rs)
{
throw (new
System.Applicat ionException(Er rDatabaseUpdate ));
}
}
}
catch (Exception ex)
{
throw (ex);
}

return;
}
Before "this.JobListDa taAdapter.Updat e(oChangeDataTa ble);" oChangeDataTabl e
contains 1 row. After the Update(), oChangeDataTabl e contains 0 row.

Does anyone knows why? The followings are some of my guesses

1. DataTable.GetCh anges() contains a collection that points to the same
DataRow as the DataTable. Hence, when Update() causes the deleted row to be
removed, oChangeDataTabl e's collection loses the removed row.

2. The part I do not understand is if oChangeDataTabl e's collection still
points to the deleted DataRow, shouldn't it still be in memory and not
garbage collected?

3. Does DataRow.Dispose () has anything to do with this?

4. How is oChangeDataTabl e's collection is smart enough to update its count
from 1 to 0?

5. Unless the original DataTable actually maintains the change data table
and DataTable.GetCh anges() simply returns a reference to this managed table?

Sorry for the bubbling here. I am typing while thinking.
--
George

[George]

I will answer my own question post here....

The side effect is caused by the AcceptChangesDu ringUpdate flag in
DataAdapter. I have been passing the table obtained from
DataTable.GetCh anges() into DataAdapter.Upd ate().

This does exactly what the specification stated, but not what I wanted.

Thanks,

--
George
"George" wrote:

Got a question about the side effect of DataAdapter.Upd ate() and
DataTable.GetCh anges().

Say I set up a DataTable and a DataAdapter in a class. Delete (Not remove)
a row in the data table and call the following method.

public void JobListDataTabl eFromAccessComm itChange()
{
System.Data.Dat aTable oChangeDataTabl e;

try
{
if (this.jobListDa taTable.HasErro rs)
{
throw (new
System.Applicat ionException(Er rDatabaseUpdate ));
}

oChangeDataTabl e = this.jobListDat aTable.GetChang es();
if (oChangeDataTab le != null)
{
this.JobListDat aAdapter.Update (oChangeDataTab le);

foreach (System.Data.Da taRow oDataRow in
oChangeDataTabl e.Rows)
{
if (oDataRow[JobDataGridView ColumnId] ==
System.DBNull.V alue)
{
this.jobListDat aTable.Clear();

this.jobListDat aAdapter.Fill(t his.jobListData Table);
break;
}
}

if (this.jobListDa taTable.HasErro rs)
{
throw (new
System.Applicat ionException(Er rDatabaseUpdate ));
}
}
}
catch (Exception ex)
{
throw (ex);
}

return;
}
Before "this.JobListDa taAdapter.Updat e(oChangeDataTa ble);" oChangeDataTabl e
contains 1 row. After the Update(), oChangeDataTabl e contains 0 row.

Does anyone knows why? The followings are some of my guesses

1. DataTable.GetCh anges() contains a collection that points to the same
DataRow as the DataTable. Hence, when Update() causes the deleted row to be
removed, oChangeDataTabl e's collection loses the removed row.

2. The part I do not understand is if oChangeDataTabl e's collection still
points to the deleted DataRow, shouldn't it still be in memory and not
garbage collected?

3. Does DataRow.Dispose () has anything to do with this?

4. How is oChangeDataTabl e's collection is smart enough to update its count
from 1 to 0?

5. Unless the original DataTable actually maintains the change data table
and DataTable.GetCh anges() simply returns a reference to this managed table?

Sorry for the bubbling here. I am typing while thinking.
--
George

[Kevin Yu [MSFT]]

Hi George,

You can call Update on jobListDataTabl e directly to update the database.
This will make things much easier. :-)

Kevin Yu
Microsoft Online Community Support

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[George]

Kevin,

Do you mean DataTable.Updat e()? I am not able to locate this public method.
Please let me know if I misundertand your previous post.

Note: Currently, I use OleDbDataAdapte r.Update(<DataT able>). It does work
as I expect.

Thanks,
--
George
"Kevin Yu [MSFT]" wrote:

Hi George,

You can call Update on jobListDataTabl e directly to update the database.
This will make things much easier. :-)

Kevin Yu
Microsoft Online Community Support

=============== =============== =============== =============== =============== =
=============== ===========
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
=============== =============== =============== =============== =============== =
=============== ===========

(This posting is provided "AS IS", with no warranties, and confers no
rights.)

[Kevin Yu [MSFT]]

No, I mean call OleDbDataAdapte r.Update(jobLis tDataTable), which means
you're right currently.

Kevin Yu
Microsoft Online Community Support

=============== =============== =============== =============== =============== =
=============== ===========
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
=============== =============== =============== =============== =============== =
=============== ===========

(This posting is provided "AS IS", with no warranties, and confers no
rights.)