void Save_tier(bool btn)
        {
            try
            {
                ITiers tiers = new Tiers();
                if (id == 0 || textBox1.Text.Equals("") || textBox2.Text.Equals("") || textBox3.Text.Equals("") ||
                    textBox4.Text.Equals("") || textBox5.Text.Equals("") || textBox6.Text.Equals(""))
                {
                    MessageBox.Show("Complete all textbox please", "Error...", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                else
                {
                    tiers.Id       = Convert.ToInt32(id);
                    tiers.Nom      = textBox1.Text.Trim();
                    tiers.Postnom  = textBox2.Text.Trim();
                    tiers.Prenom   = textBox3.Text.Trim();
                    tiers.Contact  = textBox4.Text.Trim();
                    tiers.Mail     = textBox5.Text.Trim();
                    tiers.Addresse = textBox6.Text.Trim();

                    if (btn)
                    {
                        tiers.Save(tiers); InitializeComponents();
                    }
                    else
                    {
                        tiers.Delete(id); InitializeComponents();
                    }
                }
            }catch (Exception ex) { MessageBox.Show("Error " + ex.Message); }
        }