Database

<pre lang="c#"> String intime = "";
                String outtime = "";
             
                String indatetime=System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
                String outdatetime = System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

                using (MySqlConnection con = new MySqlConnection(ConnectionString))
                {
                    String query = "select * from visitor where card_id=@id ORDER BY card_id DESC LIMIT 1";
                    MySqlCommand command = new MySqlCommand(query, con);
                    command.Parameters.AddWithValue("@id", txtAddVisitorCardId.Text);
                    con.Open();
                    using (MySqlDataReader rdr = command.ExecuteReader())
                    {
                        if (rdr.Read())
                        {
                            intime = rdr["in_time"].ToString();
                            outtime = rdr["out_time"].ToString();
                        }
                    }

                }

                if (((intime == "") && (outtime == "")) || ((intime!="")&&(outtime !="")))
                {
                    using (MySqlConnection con = new MySqlConnection(ConnectionString))
                    {
                        String query = "insert into visitor(card_id,name,age,address,id_proof,contact_person,purpose,in_time) values(@id,@name,@age,@address,@idproof,@contact,@purpose,@in)";
                        MySqlCommand command = new MySqlCommand(query, con);
                        command.Parameters.AddWithValue("@id", txtAddVisitorCardId.Text);
                        command.Parameters.AddWithValue("@name", txtAddVisitorName.Text);
                        command.Parameters.AddWithValue("@age", txtAddVisitorAge.Text);
                        command.Parameters.AddWithValue("@address", txtAddVisitorAddress.Text);
                        command.Parameters.AddWithValue("@idproof", txtAddVisitorIDProof.Text);
                        command.Parameters.AddWithValue("@contact", txtAddVisitorContactPerson.Text);
                        command.Parameters.AddWithValue("@purpose", txtAddVisitorPurpose.Text);
                        command.Parameters.AddWithValue("@in", indatetime);
                        con.Open();
                        command.ExecuteNonQuery();
                        MessageBox.Show("Visitor Added Successfully");

                    }
                }
                else if ((intime != "") && (outtime == ""))
                {
                    using (MySqlConnection con = new MySqlConnection(ConnectionString))
                    {
                        String query = "update visitor set out_time=@out where card_id=@id ORDER BY card_id DESC LIMIT 1";
                        MySqlCommand command = new MySqlCommand(query, con);
                        command.Parameters.AddWithValue("@id", txtAddVisitorCardId.Text);
                        command.Parameters.AddWithValue("@out", outdatetime);
                        con.Open();
                        command.ExecuteNonQuery();
                    }

                }
            }