Deleting rows in ADO.NET

[Dmitry Karneyev]

Hi!

I try to delete rows from the table in such way
foreach(DataRow row in MyDataSet.MyTable)
{
row.Delete();
}
and recive an error that collection is changed and enumeration is
impossible.
I guesss that foraech operator uses collection of undeleted rows and this
causes such behaviour.

Is there another approach to mark all rows in the table to deleted state?

Thanks
Dmitry

[Dmitry Karneyev]

accurate code is:

foreach(DataRow row in MyDataSet.MyTable.Rows)
{
row.Delete();
}

Dmitry

[Nicholas Paldino [.NET/C# MVP]]

Dmitry,

The easier way would be to cycle through the rows backwards (using an
index), and then call the delete method on them while you cycle backwards,
like this:

// Cycle backwards.
for (int pintIndex = MyDataSet["MyTable"].Rows.Count - 1; pintIndex >= 0;
pintIndex--)
// Delete the row.
MyDataSet["MyTable"].Rows[pintIndex].Delete();

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Dmitry Karneyev" <ka******@msn.com> wrote in message
news:ei*************@tk2msftngp13.phx.gbl...

Hi!

I try to delete rows from the table in such way
foreach(DataRow row in MyDataSet.MyTable)
{
row.Delete();
}
and recive an error that collection is changed and enumeration is
impossible.
I guesss that foraech operator uses collection of undeleted rows and this
causes such behaviour.

Is there another approach to mark all rows in the table to deleted state?

Thanks
Dmitry

[Miha Markic]

Hi Nicholas,

Actualy your way would be the only correct.
The reason is that if row is in Added RowState and you call Delete() on it,
it will be *removed* from collection and cause an exception if you are
within foreach loop like Dmitry does or index out of range if within
positive for loop.

--
Miha Markic - RightHand .NET consulting & software development
miha at rthand com
www.rthand.com

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> wrote in
message news:Ot**************@TK2MSFTNGP10.phx.gbl...

Dmitry,

The easier way would be to cycle through the rows backwards (using an
index), and then call the delete method on them while you cycle backwards,
like this:

// Cycle backwards.
for (int pintIndex = MyDataSet["MyTable"].Rows.Count - 1; pintIndex >= 0;
pintIndex--)
// Delete the row.
MyDataSet["MyTable"].Rows[pintIndex].Delete();

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Dmitry Karneyev" <ka******@msn.com> wrote in message
news:ei*************@tk2msftngp13.phx.gbl...

Hi!

I try to delete rows from the table in such way
foreach(DataRow row in MyDataSet.MyTable)
{
row.Delete();
}
and recive an error that collection is changed and enumeration is
impossible.
I guesss that foraech operator uses collection of undeleted rows and this causes such behaviour.

Is there another approach to mark all rows in the table to deleted state?
Thanks
Dmitry

[Miha Markic]

Hi Dmitry,

This is not a safe way.
See Nicholas' reply and my reply to him.

--
Miha Markic - RightHand .NET consulting & software development
miha at rthand com
www.rthand.com

"Dmitry Karneyev" <ka******@msn.com> wrote in message
news:ud**************@TK2MSFTNGP09.phx.gbl...

accurate code is:

foreach(DataRow row in MyDataSet.MyTable.Rows)
{
row.Delete();
}

Dmitry

[Frank Oquendo]

What about this?

while (myTable.Rows.Count > 0)
{
myTable.Rows[0].Delete();
}

--
There are 10 kinds of people. Those who understand binary and those who
don't.

http://code.acadx.com
(Pull the pin to reply)

[Nicholas Paldino [.NET/C# MVP]]

Frank,

That should work fine as well. The only problem with this is that you
have to be sure that the Count property is affected by the Delete, and not
just set so that the row is in a "delete" state.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Frank Oquendo" <fr****@acadxpin.com> wrote in message
news:%2****************@TK2MSFTNGP10.phx.gbl...

What about this?

while (myTable.Rows.Count > 0)
{
myTable.Rows[0].Delete();
}

--
There are 10 kinds of people. Those who understand binary and those who
don't.

http://code.acadx.com
(Pull the pin to reply)