//Cập nhật 1 phục vụ
 public Boolean UpdateWaiter(WaiterDTO lst)
 {
     try
     {
         WAITER_INFO query = (from p in Context.WAITER_INFO where p.Id == lst.ID select p).SingleOrDefault();
         query.NAME = lst.NAME;
         query.ADDRESS = lst.ADDRESS;
         query.BIRTHDAY = lst.BIRTHDAY;
         query.PHONE = lst.PHONE;
         Context.SaveChanges();
         return true;
     }
     catch (Exception ex)
     {
         throw ex;
     }
 }
        //Thêm 1 phục vụ vào danh sách
        public Boolean InsertWaiter(WaiterDTO lst)
        {
            try
            {
                WAITER_INFO newDishType = new WAITER_INFO()
                {
                    Id = Guid.NewGuid(),
                    NAME = lst.NAME,
                    ADDRESS = lst.ADDRESS,
                    BIRTHDAY = lst.BIRTHDAY,
                    PHONE = lst.PHONE
                };

                Context.WAITER_INFO.AddObject(newDishType);
                Context.SaveChanges();
                return true;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        private void tsbSave_Click(object sender, EventArgs e)
        {
            BindDataPhucVu();

            WaiterDTO dt = new WaiterDTO();
            if (FormState == FormBase.FormStateType.New)
            {
                dt.NAME = textBox3.Text.Trim();
                dt.BIRTHDAY = dateTimePicker1.Value;
                dt.ADDRESS = textBox2.Text.Trim();
                dt.PHONE = textBox1.Text.Trim();
                
                rep.InsertWaiter(dt);
            }
            else if (FormState == FormBase.FormStateType.Edit)
            {
                dt.ID = PKEY;
                dt.NAME = textBox3.Text.Trim();
                dt.BIRTHDAY = dateTimePicker1.Value;
                dt.ADDRESS = textBox2.Text.Trim();
                dt.PHONE = textBox1.Text.Trim();
                
                rep.UpdateWaiter(dt);
            }
            FormState = FormStateType.Normal;
            panel1.Enabled = false;
            tsbSave.Enabled = false;
            tsbCancel.Enabled = false;
            tbsAddNew.Enabled = true;
            tsbEdit.Enabled = true;
            tsbDelete.Enabled = true;
            LoadDataPhucVu();
        }