#region Load dataGrid
        public void loadDataGrid(string sqlQueryString) {
           OleDbCommand SQLQuery = new OleDbCommand();
                        DataTable data = null;
                        dataGridView1.DataSource = null;
                        SQLQuery.Connection = null;
                        OleDbDataAdapter dataAdapter = null;
                        dataGridView1.Columns.Clear(); // <-- clear columns
                        //---------------------------------
                        SQLQuery.CommandText = sqlQueryString;
                        SQLQuery.Connection = database;
                        data = new DataTable();
                        dataAdapter = new OleDbDataAdapter(SQLQuery);
                        dataAdapter.Fill(data); --> viene segnalato anche un errore qui!!!
                        dataGridView1.DataSource = data;
                        dataGridView1.AllowUserToAddRows = false; // remove the null line
                        dataGridView1.ReadOnly = true;
                        dataGridView1.Columns[0].Visible = true;

            dataGridView1.Columns[1].Width = 70;
            dataGridView1.Columns[2].Width = 70;
            dataGridView1.Columns[3].Width = 100;
            dataGridView1.Columns[4].Width = 150;
            dataGridView1.Columns[5].Width = 100;
    //        dataGridView1.Columns[6].Width = 100; //-->Errore nella visualizzazione della Colonna al caricamento.
            // insert edit button into datagridview
            editButton = new DataGridViewButtonColumn();
            editButton.HeaderText = "Modifica";
            editButton.Text = "Modifica";
            editButton.UseColumnTextForButtonValue = true;
            editButton.Width = 80;
            dataGridView1.Columns.Add(editButton);
            // insert delete button to datagridview
            deleteButton = new DataGridViewButtonColumn();
            deleteButton.HeaderText = "Elimina";
            deleteButton.Text = "Elimina";
            deleteButton.UseColumnTextForButtonValue = true;
            deleteButton.Width = 80;
            dataGridView1.Columns.Add(deleteButton);
        }
        #endregion