Display long Int from access to a text box

Question

I want to fill the text box with the ID of the customer name that has been selected in a combo box. I am getting error under customerID saying

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Unknown method 'GetInt32(string)'of 'System.Data.Oledb.OledbDataReader'

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this is the copy of the whole code

        private void RadMultiColumnComboBox1SelectedIndexChanged(object sender, EventArgs e)
    {
        string constring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source= RoadRunnerDB.mdb";
        string query = "select * from RoadRunnerDB.customerList where customerCompanyName = '" + radMultiColumnComboBox1 + "';";
        OleDbConnection con = new OleDbConnection(constring);
        OleDbCommand cmd = new OleDbCommand(query, con);            
        OleDbDataReader rd;
        try
        {
            con.Open();
            rd = cmd.ExecuteReader();

            while (rd.Read())
            {                             //Error is under here
                string custID = rd.GetInt32("customerID").ToString();
                radTextBox5.Text = custID;
            }
        }

        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

Answer 1

As per the msdn GetInt32(int index) takes zero-based column ordinal

so change you code from string query = "select * from RoadRunnerDB.custo..... to

string query = "select customerID from RoadRunnerDB.customerList.... 

and use GetString( int index) as msdn stated :

string custID = rd.GetString(0);