private void button3_Click(object sender, EventArgs e)
        {
           // conn.Close(); conn.Open();
            //BeginInvoke(new check_delegat(check_data));
            //MessageBox.Show(_id);
            /*MySqlCommand command = new MySqlCommand(sql, conn);
            MySqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                _id = reader["id_client"].ToString();
            }
            MessageBox.Show(_id);
            reader.Close();
            conn.Close();*/

            //conn.Close(); conn.Open();
            using (MySqlConnection conn1 = new MySqlConnection(connStr))
            {
                conn1.Close();
                conn1.Open();
                string sql2 = "INSERT INTO `client_msg` VALUES (NULL, @id_client, @msg)";
                MySqlCommand command = new MySqlCommand(sql2, conn1);
                command.Parameters.AddWithValue("@id_client", "1");
                command.Parameters.AddWithValue("@msg", textBox5.Text);
                command.ExecuteNonQuery();
                conn1.Close();
            }
        }