Web Service via Data Access Object Pattern

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;
using System.IO;
using System.Xml.Serialization;
using System.Xml;
using AndrewGolik.DaoTraining.TransferObjects;
using AndrewGolik.DaoTraining.Common.Utilities;

namespace AndrewGolik.DaoTraining.DataAccessLayer.XmlRepository 
{

    public class XmlCustomerDao:CustomerDao
    {
        private Object thisLock = new Object();
                   
        public  int CreateCustomer(Customer customer)
        {


            lock (thisLock)
            {
                
                XmlDocument xmlCustomers = new XmlDocument();
                xmlCustomers.Load(XmlDaoFactory.PathToCustomersFile);
                //generate the new id for the customer
                XmlNode xmlLastGeneratedId = xmlCustomers.DocumentElement.Attributes.GetNamedItem("LastGeneratedId");
                int lastGeneratedIdValue = Convert.ToInt32(xmlLastGeneratedId.Value) + 1;
                xmlLastGeneratedId.InnerText = lastGeneratedIdValue.ToString();
                //assign the new generated id to the customer then serialize it to xml
                customer.CustomerID = lastGeneratedIdValue;
                XmlDocument xmlCustomer = Serialization.FillXmlDocFromObject<Customer>(customer);
                //import new customer xml to customers list
                xmlCustomers.DocumentElement.AppendChild(xmlCustomers.ImportNode(xmlCustomer.DocumentElement,true));
                xmlCustomers.Save(XmlDaoFactory.PathToCustomersFile);
                return lastGeneratedIdValue;

            }
            
          
           
                 
        }

        public  bool DeleteCustomer(int customerID) 
        {
            lock(thisLock)
            {   //remove all related orders
                //note: this calling is optional. If the datasource supports "cascade removing related records"
                //you can just ignore this calling. For instance, it's ignored in MsSqlDao
                 
                DeleteOrders(customerID);
                XmlDocument xmlDoc = new XmlDocument();
                xmlDoc.Load(XmlDaoFactory.PathToCustomersFile);
                XmlNode xmlCutomerNode = xmlDoc.DocumentElement.SelectSingleNode("Customer[CustomerID = " + customerID + "]");
                if (xmlCutomerNode != null)
                {
                    xmlCutomerNode.ParentNode.RemoveChild(xmlCutomerNode);
                    xmlDoc.Save(XmlDaoFactory.PathToCustomersFile);
                    return true;
                }
                else
                    return false;
            }
        }
        
        public bool DeleteOrders(int customerID) 
        {

            lock (thisLock)
            {

                XmlDocument xmlOrders = new XmlDocument();
                xmlOrders.Load(XmlDaoFactory.PathToOrdersFile);
                XmlNodeList orders = xmlOrders.DocumentElement.SelectNodes("Order[CustomerID="+customerID+"]");
                if (orders.Count == 0)
                    return false;
                for (int index=0;index < orders.Count;index++)
                {
                    orders[index].ParentNode.RemoveChild(orders[index]);
                }
                xmlOrders.Save(XmlDaoFactory.PathToOrdersFile);
                return true;
        
            }
            
        }
       
      
        public  bool UpdateCustomer(Customer customer) 
        {



            lock (thisLock)
            {   //first remove customer to update
                if (DeleteCustomer(customer.CustomerID))
                {
                    XmlDocument xmlCustomer = Serialization.FillXmlDocFromObject<Customer>(customer);
                    //import customer xml updated to customers list
                    XmlDocument xmlCustomers = new XmlDocument();
                    xmlCustomers.Load(XmlDaoFactory.PathToCustomersFile);
                    xmlCustomers.DocumentElement.AppendChild(xmlCustomers.ImportNode(xmlCustomer.DocumentElement, true));
                    xmlCustomers.Save(XmlDaoFactory.PathToCustomersFile);
                    return true;
                }
                else 
                 
                    return false;
                 
            }


          

        }

        public List<Customer> GetCustomers() 
        { 

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(XmlDaoFactory.PathToCustomersFile);
            XmlNodeList xmlCustomerList = xmlDoc.DocumentElement.SelectNodes("Customer");
            List<Customer> customers = new List<Customer>();
            for(int index=0; index < xmlCustomerList.Count; index++)
            {
                XmlDocument xmlCustomer = new XmlDocument();
                xmlCustomer.LoadXml(xmlCustomerList[index].OuterXml);
                Customer customer =  Serialization.FillObjectFromXMLDoc<Customer>(xmlCustomer);
                customers.Add(customer);

            }
            return customers;

        }
       
    }
}