private void griglia_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            int id_articolo = (int)listaArticoli.griglia.Rows[e.RowIndex].Cells["id_articolo"].Value;
            if (id_articolo >0)
            {
                DataGridViewRow currRow = new DataGridViewRow();
                currRow=listaArticoli.griglia.SelectedRows[0];

                articoli_mod am = new articoli_mod();
                am.Text = "Modifica Articolo";
                am.txtNome.Text = currRow.Cells["nome"].Value.ToString();
                am.txtPrezzo.Text = currRow.Cells["prezzo"].Value.ToString();
                am.cbFornitore.DataSource = from f in idc.tb_fornitori select f;
                am.cbFornitore.SelectedValue = currRow.Cells["fornitore"].Value;

                if (am.ShowDialog(this) == DialogResult.OK)
                {
                    currRow.Cells["nome"].Value = am.txtNome.Text;
                    currRow.Cells["prezzo"].Value = am.txtPrezzo.Text;
                    currRow.Cells["fornitore"].Value = am.cbFornitore.SelectedValue.ToString();
                }

            }
        }