Subject Re: Object reference not set to an instance of an object
Author clemenslinders
--- In firebird-support@yahoogroups.com, "clemenslinders"
<clemenslinders@y...> wrote:
> LS,
>
> I use a grid to display my data. This all works fine, but as soon
as
> I try to use the update command, than I get the error: Object
> reference not set to an instance of an object. I've read the
> Firebird book, but I cannot find my answer there.
>
> I'm using:
> -XtraGrid (latest version 2.05) from devex as my datagrid.
> -Firebird 1.5
> -Windows XP pro
>
> I tried using
>
> ColumnView view = gridControl1.FocusedView as ColumnView;
> view.CloseEditor();
> view.UpdateCurrentRow();
> sqlDataAdapter1.Update(myDataSet, "MyTable");
>
> and
>
> dataAdapter.Update(dataTable);
>
> Both ways give an error and do not update my table.
>
> I have a gridControl1 with 7 columns.
>
> The select statement is:
> private void uiButton3_Click(object sender, System.EventArgs
e)
>
> {
>
> TableFM.Clear();
>
> fbCommand1.CommandText=@"select
>
t2.songname,t4.artistname,t3.componersname,t1.titelsong_yesno,t1.rema
> rk,t2.songnr,t1.movienr
>
> from songs t2 join artist t4
>
> on t2.artistnumber=t4.artistnr
>
> join componer t3
>
> on t2.componernumber=t3.componernr
>
> join moviemusic t1
>
> on t1.songnumber=t2.songnr
>
> where t1.movienr="+editBox1.Text;
>
> fbDataAdapter1.Fill(TableFM);
>
> }
>
> The DataSource for gridView1=TableFM, the
> DataAdapter=fbDataAdapter1, the DataSet=MusicFileDS with the
> Argument Tables named TableFM (Connection=fbConnection1)
>
> Because the select statement select values from more than one
table
> only a select-statement can be generated. So Update, Insert and
> Delete statements have to be programmed manually.
>
> To be sure that the problem isn't in the update statement I gave
the
> update statement the following value:
>
> fbCommand3.CommandText="update songs set songname=\"├Łesterday\"
> where songnr=1";
>
> In the Table songs, the field songnr is the primary key and there
> are a number of songs listed. So changing the value of the first
> songnr to songname=yesterday should not be a problem.
>
>
>
> I put my update command in the griedView_RowUpdated event, which
> does fire when an update has occured
>
> private void gridView1_RowUpdated(object sender,
> DevExpress.XtraGrid.Views.Base.RowObjectEventArgs e)
>
> {
>
> //editBox1.Text=fbCommand3.ExecuteNonQuery().ToString();
>
> ColumnView view = gridControl1.FocusedView as ColumnView;
>
> view.CloseEditor();
>
> view.UpdateCurrentRow();
>
> fbDataAdapter1.Update(FilmMuziekDS.Tables["TableFM"]);
>
> //fbDataAdapter1.Update(FilmMuziekDS, "TableFM");// (both
these
> lines give same error)
>
> }
>
> I get the following error:
>
> Additional information: Object reference not set to an instance of
> an object.
>
>
>
>
> I also tried: editBox1.Text=fbCommand3.ExecuteNonQuery().ToString
();
>
> in stead of the bottom lines. I than get a different error
> (Additional information: Connection must valid and open) but it
> doesn't help. I even put fbConnection.Open in front of these lines
> but the error remained.
>
> Ofcourse I will probably make a mistake somewhere or I'm just not
> looking into the right direction.
>
> I would appreciate it if anyone could help me.
>
> Kind regards,
>
>
> Clemens Linders

At first I checked the posted messages back to 30.000. After I
mailed this question I just looked further and found something that
helped me.

Apperently placing it in a transaction is mandatory furthermore I
needed to end with commiting the transaction.

The working code:
private void gridView1_RowUpdated(object sender,
DevExpress.XtraGrid.Views.Base.RowObjectEventArgs e)
{
ColumnView view = gridControl1.FocusedView as
ColumnView;
view.CloseEditor();
view.UpdateCurrentRow();
fbConnection1.Open();
FbTransaction myTxn = fbConnection1.BeginTransaction
();
string myUpdateQuery ="update songs set
songs.songname='yesterday' where songnr=1";
FbCommand myFbCommand = new FbCommand(myUpdateQuery,
fbConnection1,myTxn);
myFbCommand.ExecuteNonQuery();
myTxn.Commit();
fbConnection1.Close();
}

Thanks anyway and maybe someone in the future is helped by this.

Kind regards,


Clemens Linders