Question

I have a connection class laki this:

 public static OleDbConnection connection = new OleDbConnection();
    public string sorgu;
    public static string server;
    public static string userId;
    public static string catalog;
    public static string password;
    public DataSet ds = new DataSet();

    public bool Open()
    {
        try
        {
            if (connection.State != ConnectionState.Open)
            {

                connection.ConnectionString = "Provider=SQLOLEDB.1" +
                                               ";Password=" + password +
                                               ";Persist Security Info=True" +
                                               ";User ID=" + userId +
                                               ";Initial Catalog=" + catalog +
                                               ";Data Source=" + server;

                connection.Open();
                return true;
            }
            else
            {                    
                return true;
            }                   


        }
        catch (Exception ex)
        {
            MessageBox.Show("Sistem Mesajı:" + ex.Message, "Hata", MessageBoxButtons.OK, MessageBoxIcon.Error);
            return false;
        }

    }


    public void CloseConnection()
    {
        if (connection.State == ConnectionState.Open)
        {
            connection.Close();
        }

    }


    public DataTable Dt(string query)
    {

        DataTable dt = new DataTable();
        if (Open())
        {
            OleDbDataAdapter da = new OleDbDataAdapter(query, connection);
            try
            {
                da.Fill(dt);

            }
            catch (Exception ex)
            {
                MessageBox.Show("Sistem Mesajı:" + ex.Message, "Hata", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
        //baglanti.Close();
        return dt;


    }

and this is my code which I get the values in a windows form

ConnectionClassOleDb cc = new ConnectionClassOleDb();
sorgu = " SELECT * FROM tblFiyatlandirma WHERE " +
                    " musteriNo=" + musteriNo +
                    " AND musteriTipId=" + musteriTipId;

            nudSiparisMetresi.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["siparisMetresi"]);
            nudKar.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["kar"]);
            nudKumasEni.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["kumasEni"]);
            nudMamulFire.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["mamulFire"]);
            nudMamulKumasKari.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["mamulKumasKar"]);
            nudNakliyeUcreti.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["nakliye"]);
            nudKomisyon.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["komisyon"]);
            nudTarakEni.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["tarakEni"]);
            nudTarakNo.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["tarakNo"]);
            nudTarakGecisi.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["tarakGecisi"]);
            nudAtkiFiyat.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["atkiFiyati"]);
            nudAtkiSikligi.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["atkiSikligi"]);
            nudAnalizNo.Value = Convert.ToDecimal(cc.Dt(sorgu).Rows[0]["analizNo"]);

the codes are work but in every cc.Dt(sorgu).Rows[0] row cc clas is going to connection class again and doing a new query. what is wrong?

Answer 1

Because every time you call ‘Dt’ you create a new datatable and adapter and fill the datatable with the adapter. This will cause the query to be executed on each call.

You should store the returned DataTable in a local variable and do your operations like ‘Rows’ on that instead of calling your DB class every time.

So:

DataTable dt = cc.Dt(sorgu);

and then use

dt.Rows[0]["siparisMetresi"]

instead of

cc.Dt(sorgu).Rows[0]["siparisMetresi"]