class to open its database

ago2486

public class ConnectionDB
{

    // Declaration des objets sql
    public OleDbConnection sql\_con;
 
    // declaration de la methode connecter
    public void CONNECTER()
    {
        try
        {
            string connetionString = null;
            //connection à la base de donnée avec mot de passe
            connetionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data source=" + Application.StartupPath + @"\\DB\_CaisseEnregistreuse.mdb;Persist Security Info=True;Jet OLEDB:Database Password=B@sta08091987";
            sql\_con = new OleDbConnection(connetionString);
            sql\_con.Open();
            
        }
        catch (Exception ex)
        {
            MessageBox.Show("Erreur de connexion à la base donnée" + ex.ToString());
        }

        
    }

    // declaration de la methode deconnecter
    public void DECONNECTER()
    {
        try
        {

            if (sql\_con.State == ConnectionState.Open)
            {

                sql\_con.Close();
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show("Erreur de deconnexion à la base donnée" + ex.ToString());
        }
    }

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();

    }

ConnectionDB d = new ConnectionDB();

using (OleDbCommand cmbox = d.sql\_con.CreateCommand())
            {
                cmbox.CommandText = "SELECT Code\_article FROM Catalogue";
                d.sql\_con.Open();
                d.DR = cmbox.ExecuteReader();

                try
                {
                    while (d.DR.Read())
                    {
                        CmbRef\_Produit.Items.Add(d.DR\["Code\_article"\]).ToString();
                    }

                    //si le textbox est vide
                    if (string.IsNullOrWhiteSpace(CmbRef\_Produit.Text ))
                    {
                        // Message box

                        Lbl\_affich\_TxtQteStock.Text = "";
                        Lbl\_Affich\_Designation.Text = "";
                        Lbl\_Affich\_PrixUnitaire.Text = "";
                    }

                }
                catch (Exception ex)

Lost User

You need to show the code that uses the CONNECTER method.

ago2486

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();

    }

ConnectionDB d = new ConnectionDB();

using (OleDbCommand cmbox = d.sql\_con.CreateCommand())
            {
                cmbox.CommandText = "SELECT Code\_article FROM Catalogue";
                d.CONNECTER.Open(); //\*\*\*\*i have an error here\*\*\*\*
                d.DR = cmbox.ExecuteReader();

                try
                {
                    while (d.DR.Read())
                    {
                        CmbRef\_Produit.Items.Add(d.DR\["Code\_article"\]).ToString();
                    }

                    //si le textbox est vide
                    if (string.IsNullOrWhiteSpace(CmbRef\_Produit.Text ))
                    {
                        // Message box

                        Lbl\_affich\_TxtQteStock.Text = "";
                        Lbl\_Affich\_Designation.Text = "";
                        Lbl\_Affich\_PrixUnitaire.Text = "";
                    }

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

                    d.DECONNECTER.Close();

                }
            }

        }

}

ago2486

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();

    }

ConnectionDB d = new ConnectionDB();

using (OleDbCommand cmbox = d.sql\_con.CreateCommand())
            {
                cmbox.CommandText = "SELECT Code\_article FROM Catalogue";
                d.CONNECTER();// i have an error here
                d.DR = cmbox.ExecuteReader();

                try
                {
                    while (d.DR.Read())
                    {
                        CmbRef\_Produit.Items.Add(d.DR\["Code\_article"\]).ToString();
                    }

                    //si le textbox est vide
                    if (string.IsNullOrWhiteSpace(CmbRef\_Produit.Text ))
                    {
                        // Message box

                        Lbl\_affich\_TxtQteStock.Text = "";
                        Lbl\_Affich\_Designation.Text = "";
                        Lbl\_Affich\_PrixUnitaire.Text = "";
                    }

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

                    d.DECONNECTER();

                }
            }

        }

}

Lost User

I am not sure that the sequence of commands is correct. Try this:

using (ConnectionDB d = new ConnectionDB())
{
d.CONNECTER();

using (OleDbCommand cmbox = d.sql\_con.CreateCommand())
{
    cmbox.CommandText = "SELECT Code\_article FROM Catalogue";

    // remaining code
}
d.DECONNECTER();

}

OriginalGriff

First off, don't hard code connection strings - they need to be in a config file or similar, if only so you don't release the password in clear text with your app... Second, never store databases in your app directory: although it works in development, it will fail in production as the application folder rarely has write permissions anymore for anti-virus reasons. See here: Where should I store my data?[^] for some better ideas. Thirdly, you are much, much better off creating your Connection object in your code when you need it inside a using block, as they are scarce resources and should be Disposed when you are finished with them:

using (SqlConnection con = new SqlConnection(strConnect))
{
con.Open();
using (SqlCommand cmd = new SqlCommand("SELECT Age, Description FROM myTable WHERE ID = @ID", con))
{
cmd.Parameters.AddWithValue("@ID", myTextBox.Text);
using (SqlDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
int age = (int) reader["Age"];
string desc = (string) reader["Description"];
Console.WriteLine($"{age}\n{desc}");
}
}
}
}

That way, whatever happens to your code, the objects will be closed and disposed for you automatically. Fourthly, although you are trying to separate the DB from the form (which is a good idea) don't use MessageBox to report problems with DB related stuff - it makes too many assumptions about how your code will be used. Error handling and reporting is the province of the Presentation Layer, not the Data Layer: there is no guarantee that the user will be able to see a MessageBox! Let the code that calls the DB stuff handle errors - it can report or not, but it may log instead, or just terminate what it is doing. Your way, the user gets the MessageBox, then your app crashes because the connection isn't open anyway.

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!<

ago2486

Thanks i will try it and you will get back

ago2486

I try and the error comes from me thank you very much mmister it works.

ago2486

thank you sir message well received. I haven't tried the configuration file side for the connection to the database yet, but I will study it and see if I can manage it.

ago2486

public class ConnectionDB
{

    // Declaration des objets sql
    public OleDbConnection sql\_con;
    public OleDbCommand sql\_cmd;
    public OleDbDataAdapter DB;
    public DataSet DS = new DataSet();
    public DataTable DT = new DataTable();
    public OleDbDataReader DR;
    public string connetionString = null;

    // declaration de la methode connecter
    public void CONNECTER()
    {                           
            //connection à la base de donnée avec mot de passe
            connetionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data source=" + Application.StartupPath + @"\\DB\_CaisseEnregistreuse.mdb;Persist Security Info=True;Jet OLEDB:Database Password=B@sta08091987";
            sql\_con = new OleDbConnection(connetionString);
    }

    // declaration de la methode deconnecter
    public void DECONNECTER()
    {
        

            if (sql\_con.State == ConnectionState.Open)
            {

                sql\_con.Close();
            }
        
       
    }

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();



    }
    ConnectionDB d = new ConnectionDB();

private void LoadDB()
{
using (OleDbConnection sql_con = new OleDbConnection(d.connetionString))
{
sql_con.Open();
using (OleDbCommand sql_cmd = d.sql_con.CreateCommand())
{
string CommandText = "SELECT * FROM Detail_temp";
d.DB = new OleDbDataAdapter(CommandText, d.sql_con);
d.DS.Reset();
d.DB.Fill(d.DS);
d.DT = d.DS.Tables[0];
dataGridView1.DataSource = d.DT;
d.DECONNECTER();
}
}
}

private void Form1_Load(object sender, EventArgs e)
{

        try
        {
            
            LoadDB();
            d.sql\_con.Open();
            TxtQteCmd.Text = "1";
            Lbl\_Affich\_TotalCmd.Text = "0";
            LblAfficDate.Text = DateTime.Now.ToString(); 

            using (OleDbCommand cmbox = d.sql\_con.CreateCommand())
            {
                cmbox.CommandText = "SELECT Code\_article FROM Catalogue";