C#

public class StringAndInt
{
    public string myString;
    public int myInt;
    public StringAndInt(string myString, int myInt)
    {
        this.myString = myString;
        this.myInt = myInt;
    }
}

StringAndInt[] myArray = new StringAndInt[] { new StringAndInt("String", 0), new StringAndInt("String", 1), new StringAndInt("String", 2) };

StringAndInt myArray[] = {{"String", 0}, {"String", 1}, {"String", 2}};

StringAndInt[] constructArray(string myString, int myInt)
{
    return new StringAndInt[] { new StringAndInt(myString, myInt) };
}

StringAndInt[] constructArray(string myString0, int myInt0, string myString1, int myInt1)
{
    return new StringAndInt[] { new StringAndInt(myString0, myInt0), new StringAndInt(myString1, myInt1) };
}

StringAndInt[] constructArray(string myString0, int myInt0, string myString1, int myInt1, string myString2, int myInt2)
{
    return new StringAndInt[] { new StringAndInt(myString0, myInt0), new StringAndInt(myString1, myInt1), new StringAndInt(myString2, myInt2) };
}
.
.
.
StringAndInt[] myArray = constructArray("String", 0, "String", 1, "String", 2);

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)
                    {
                        MessageBox.Show(ex.ToString());

                        d.sql_con.Close();

                    }
                }

            }

}

Quote:

I created a ConnectionDB class and 2 CONNECT and DISCONNECT methods.
I needed to open the database so I called the CONNECT method but I have an error telling me that my database is still closed so I change to sql-con.open and it works.
So my question is: Why and what is the difference.