C# SqlDataReader No data exists for the row/column

Question

I've been away from programming for a while but recently I've got a need for it.

I have a problem with SQL DataReader using Sql Server Compact Edition 4.0 (VS2012 Built-in).

string connstring = "Data Source=C:\\..(Path Here)..\\VacationsDB.sdf";
SqlCeConnection conn = new SqlCeConnection(connstring);
string strSQL = "SELECT * FROM Vacation WHERE VacationNo = @val";

using (SqlCeCommand cmd = new SqlCeCommand(strSQL, conn))
{
    //read search value from from text field
    cmd.Parameters.AddWithValue("@val", vacationno_txt.Text);
    conn.Open();

    SqlCeDataReader reader = cmd.ExecuteReader();
    fname_txt.Text = reader.GetString(0);
    mname_txt.Text = reader.GetString(1);
    /*
     * .. snip
     */
    vacationno_txt.Text = reader.GetString(11);
    conn.Close();
}

I keep getting the error: "InvalidOperationException was Unhandled. No data exists for the row/column." And the error points at fname_txt.Text = reader.GetString(0);

But there is actually data there because the "Submit" button with all it's code is working and I've checked it in the database table itself.

Any tips? Thank you.

Answer 1

DataReaders start out before the first row.

To read from the first row, call Read() once.
If there is no first row, Read() will return false .

Answer 2

You need to move the reader's (row) position first. And close it when you no longer need it.

...
using(SqlCeDataReader reader = cmd.ExecuteReader())
{
    if (reader.Read())
    {
        fname_txt.Text = reader.GetString(0);
        mname_txt.Text = reader.GetString(1); . . . 
        vacationno_txt.Text = reader.GetString(11);
    }
}
...

Answer 3

Use new datareader if showing 'No Data exist for the Row/Column'

OleDbCommand cmdsearch2 = new OleDbCommand("Select * from tbl_quotation where quotationno = @qno ", con); cmdsearch2.Parameters.AddWithValue("@qno", txt_quotationno.Text); OleDbDataReader drr = cmdsearch2.ExecuteReader();

            if (drr.HasRows)
            {
                while (drr.Read())
                {
                    cmb_customername.Text = drr["customername"].ToString();
                    txt_revno.Text = drr["revno"].ToString();
                    dtp_qdate.Text = drr["qdate"].ToString();
                    txt_paymentterms.Text = drr["paymentterms"].ToString();
                    txt_delivery.Text = drr["delivery"].ToString();
                    txt_freight.Text = drr["freight"].ToString();
                    txt_quotationvalidity.Text = drr["validity"].ToString();


                }
            }
            drr.Close();