Class employee

Selamat pagi!
perjalanan kita akan kita lanjutkan dengan membuat class employee. class ini untuk mengolah data pegawai. karena pegawai mempunyai jabatan dan kantor cabang maka kita akan menggabungkannya
inilah codinnya

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MySql.Data.MySqlClient;
using System.Windows.Forms;

namespace Core_Inventaris
{
    public class Employee
    {
        // variable definition
        Connection Connetion = new Connection();
        SystemCore SystemCorex = new SystemCore();
        MySqlDataReader Reader;
        public EmployeeComplete getData()
        {
            // function for get all employee data from database server
            EmployeeComplete EmployeeComplete = new EmployeeComplete();
           
            //Employ data
            List<EmployeeData> EmployeeDatas = new List<EmployeeData>();
            Reader = Connetion.selectTable("select * from Employee order by id");
           
            while (Reader.Read())
            {
                EmployeeData EmployeeData = new EmployeeData();
                EmployeeData.Id = Reader.GetString(0);
                EmployeeData.Name = Reader.GetString(1);
                EmployeeData.BrithDate = int.Parse(Reader.GetString(2));
                EmployeeData.Address = Reader.GetString(3);
                EmployeeData.JoinDate = int.Parse(Reader.GetString(4));
                EmployeeData.Occupation = Reader.GetString(5);
                EmployeeData.BranchOffice = Reader.GetString(6);
                EmployeeDatas.Add(EmployeeData);
            }
            Reader.Close();

            //Occupation
            List<OccupationData> OccupationDatas = new List<OccupationData>();
            Reader = Connetion.selectTable("select * from Occupation order by id");
           
            while (Reader.Read())
            {
                OccupationData OccupationData = new OccupationData();
                OccupationData.Id = Reader.GetString(0);
                OccupationData.OccupationName = Reader.GetString(1);
                OccupationData.Explaination = Reader.GetString(2);
                OccupationDatas.Add(OccupationData);
            }
            Reader.Close();

            //Branch office data
            List<BranchOfficeData> BranchOfficeDatas = new List<BranchOfficeData>();
            Reader = Connetion.selectTable("select * from branchoffice order by id");
          
            while (Reader.Read())
            {
                BranchOfficeData BranchOfficeData = new BranchOfficeData();
                BranchOfficeData.Id = Reader.GetString(0);
                BranchOfficeData.BranchName = Reader.GetString(1);
                BranchOfficeData.Address = Reader.GetString(2);
                BranchOfficeData.Phone = Reader.GetString(3);
                BranchOfficeDatas.Add(BranchOfficeData);
            }
            Reader.Close();

            EmployeeComplete.ED = EmployeeDatas;
            EmployeeComplete.OD = OccupationDatas;
            EmployeeComplete.BOD = BranchOfficeDatas;

            return EmployeeComplete;
        }       

        public bool toServer()
        {
            // function for chekking connection to database server
            List<string> Database = Connetion.readSever();

            try
            {
                if (Connetion.connection(Database[0], Database[1], Database[2]))
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            catch(Exception e)
            {
                MessageBox.Show(e.Message);
                return false;
            }
        }

        public string deleteData(string ID)
        {
            // delete query
            Reader = Connetion.selectTable("Delete from Employee where id='" + ID + "'");
            Reader.Close();
            return "Deleted!";
        }

        public string insertData(string ID, string Name, int BirthDate, string Address, int JoinDate, string Occupation, string BranchOfiice)
        {
            // insert data query
            Reader = Connetion.selectTable("INSERT INTO employee(ID, Name, BirthDate, Address, JoinDate, Occupation, BranchOffice) VALUES ('" + ID +
                        "','" + Name + "'," + BirthDate + ",'" + Address + "'," + JoinDate + ",'" + Occupation + "','" + BranchOfiice + "')");
            Reader.Close();
            return "Data Saved!";
        }

        public string updatetData(string ID, string Name, int BirthDate, string Address)
        {
            // update data query
            Reader = Connetion.selectTable("update Employee set Name = '" + Name + "', BirthDate='" + BirthDate +
                    "', address = '" + Address + "' where id = '" + ID + "'");
            Reader.Close();
            return "Data Update!";
        }
    }
   
}