Re: deleting row from dataset

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Would my deleting a row change row that the index is pointing ?

For example, if I deleted row 10, would row 11 now be pointing at the old row 12? This would be a problem since I would miss checking the old row 11 for my criteria.


No, not even for standard list: when you start at index N, toward 1, so deleting M, won't make you miss any record below since the next loop execution will look for M-1, the element below it.

Note that HERE, it is very unlikely that you effectively DELETE anything! Indedd, it is quite probably that you ONLY mark the row state as deleted, nothing more, AND when you will synchronize back the row, ADO Net will read that data, see its status as deleted, and will THEN try to delete it IN THE DATABASE, and finally, ONLY AFTER THAT, would it be deleted it from your side. BUT only after a resychronisation, NOT immediatly: If it was to simply delete it, from your side, BEFORE making any synchronization with the database, how would ADO Net be aware of that it has to delete it! Furthermore, yconsider that ou can still filter / see deleted stuff (as long as you don't resynch), with the overload indexer: dr[fieldName, DataRowVersion ].

Furthermore, if ever you re-execute again your loop after a first "delete" pass, BEFORE you resynchronize it with the database, you will likely get an error trying to read a field from a row marked as deleted! So, *if* this is a possibility, check the rowState before: trying to read the field:

if ( dr.RowState != DataRowState.Deleted && (string)dr["tagName"] != "CITY.1")
{
...
}


Sure, that extra test is not necessary if you resych your data immediatly after this loop.


I am clueless about why foreach does not allow the delete(), since it deletes nothing (if my point of view is correct). Sure, standard foreach do not allow standard delete, so, maybe it is more "by design" for uniformity, than for real need. I can be wrong, though, have never seen the IL code behind that delete(), neither the one behind foreach, by the way.




Vanderghast, Access MVP


"tshad" <toms@xxxxxxxx> wrote in message news:Ou9A3U46JHA.4404@xxxxxxxxxxxxxxxxxxxxxxx

"Martin Honnen" <mahotrash@xxxxxxxx> wrote in message news:%23wlruP46JHA.1564@xxxxxxxxxxxxxxxxxxxxxxx
tshad wrote:

I tried:

foreach (DataRow dr in AppSettings.ds.Tables["form"].Rows)
{
if ((string)dr["tagName"] != "CITY.1")
{
dr.Delete();
}
}

But get an error:

Collection was modified; enumeration operation might not execute.

How else would I do this?

DataTable table = AppSettings.ds.Tables["form"];
for (int i = table.Rows.Count - 1; i >= 0; i--)
{
DataRow row = table.Rows[i];
if ((string)row["tagName"] != "CITY.1")
{
row.Delete();
}
}


Would my deleting a row change row that the index is pointing ?

For example, if I deleted row 10, would row 11 now be pointing at the old row 12? This would be a problem since I would miss checking the old row 11 for my criteria.

I did also try cloning the table and move the data that way:

DataTable dt = new DataTable();
dt = AppSettings.ds.Tables["form"].Clone();

foreach (DataRow dr in AppSettings.ds.Tables["form"].Rows)
{
if ((string)dr["tagName"] == "CITY.1")
{
dt.ImportRow(dr);
}
}

AppSettings.ds.Tables.Remove(AppSettings.ds.Tables["form"]);

This seems to work, but how would I move the new datatable (dt) into the dataset.

Also, is there a way to move the datatable in Table Position 0? This is not necessary as I access the table by name but curious if I can.

This is needed as I am adjusting the datatable to run it through some existing code that expects a dataset.

Thanks,

Tom

--

Martin Honnen --- MVP XML
http://msmvps.com/blogs/martin_honnen/



.

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