handle exception error in listview

[RomeoX]

Hi everybody,

Actually I'm trying to do small form that has a textbox for BARCODE which when I scan an item it will add on my listview but I recieved this error that I don't know what went wrong in my code

"System.NullRef erenceException : Object reference not set to an instance of an object."

private void text1_down(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {


                try
                {

                    OracleDataAdapter xx = new OracleDataAdapter("SELECT * FROM POS WHERE barcode = " + this.textBox1.Text, conn);
                    ww = cmnd.ExecuteReader();
                    DataSet DS = new DataSet();
                    xx.Fill(DS, "pos");
                    DataTable dtable = DS.Tables["pos"];

                    // Display items in the ListView control
                    for (int i = 0; i < dtable.Rows.Count; i++)
                    {
                        DataRow drow = dtable.Rows[i];

                        // Only row that have not been deleted
                        if (drow.RowState != DataRowState.Deleted)
                        {
                            // Define the list items
                            ListViewItem lvi = new ListViewItem(drow["product_name"].ToString());
                            lvi.SubItems.Add(drow["price"].ToString());

                            // Add the list items to the ListView
                            listView2.Items.Add(lvi);
                        }
                    }

                }

                catch (Exception error)
                {
                    MessageBox.Show(error.ToString());
                }
            }
        }

Could anyone help me to fix this code

[PsychoCoder]

What line does the error occur on. Set a breakpoint on line 3 and use F11 to step through your code to find out where the error is occurring.

[RomeoX]

First of all, thank you very much for replying to my topic. Actually I changed the code to use the button instead of barcode, it mentioned the error in line 74 which is FOR loop line seems doesn't catch the any thing from the database,

for (int i = 0; i < dtable.Rows.Cou nt; i++)

private void button1_Click(object sender, EventArgs e)
        {
            try
            {

                OracleDataAdapter xx = new OracleDataAdapter("Select * From localpos where brcod = 6281014472210", conn);
                DataSet DS = new DataSet();
                xx.Fill(DS);
                DataTable dtable = DS.Tables["localpos"];

                // Display items in the ListView control
                for (int i = 0; i < dtable.Rows.Count; i++)
                    
                {
                    DataRow drow = dtable.Rows[i];

                    // Only row that have not been deleted
                    if (drow.RowState != DataRowState.Deleted)
                    {
                        // Define the list items
                        ListViewItem lvi = new ListViewItem(drow["p_name"].ToString());
                        lvi.SubItems.Add(drow["p_price"].ToString());

                        // Add the list items to the ListView
                        listView2.Items.Add(lvi);
                    }
                }

            }

            catch (Exception er)
            {
                MessageBox.Show(er.ToString());
            }
        }