An Address Book Application Made in MVVM For Metro Style App in Windows 8 Part 2

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Mvvm3_Basic.Model;
using System.Xml;
using System.Xml.Linq;
using Windows.ApplicationModel;
using Windows.Data.Xml.Dom;
using Windows.Storage;
using System.IO;

namespace Mvvm3_Basic.ViewModel
{
    class DB
    {
        public ObservableCollection<Contact> contactlist { get; set; }

        public async void GetContactList()
        {
            var sf = await Package.Current.InstalledLocation.GetFileAsync(@"ContactXML.xml");
            var file = await sf.OpenAsync(FileAccessMode.Read);
            Stream inStream = file.AsStreamForRead();

            XDocument xdoc = XDocument.Load(inStream);
            var contacts = (from contact in xdoc.Descendants("Contact")
                            select new
                            {
                                CGuid = contact.Element("CGuid").Value,
                                Name = contact.Element("Name").Value,
                                Email = contact.Element("Email").Value
                            });

            if (contactlist == null) contactlist = new ObservableCollection<Contact>();
            contactlist.Clear();

            foreach (var c in contacts)
            {
                contactlist.Add(new Contact { CGuid = c.CGuid, Name = c.Name, Email = c.Email });
            }
        }

        public async void Save(Contact c)
        {
            var sf = await Package.Current.InstalledLocation.GetFileAsync(@"ContactXML.xml");
            XmlDocument xmlDoc;
            using (var stream = await sf.OpenAsync(FileAccessMode.ReadWrite))
            {
                xmlDoc = await XmlDocument.LoadFromFileAsync(sf);
                XmlElement root = xmlDoc.DocumentElement;
                XmlElement xe = xmlDoc.CreateElement("Contact");
                XmlElement cguid = xmlDoc.CreateElement("CGuid");
                cguid.InnerText = Guid.NewGuid().ToString();
                XmlElement name = xmlDoc.CreateElement("Name");
                name.InnerText = c.Name;
                XmlElement email = xmlDoc.CreateElement("Email");
                email.InnerText = c.Email;
                xe.AppendChild(cguid);
                xe.AppendChild(name);
                xe.AppendChild(email);
                root.AppendChild(xe);
            }
            if (xmlDoc != null)
                await xmlDoc.SaveToFileAsync(sf);
        }

        public async void Update(Contact c)
        {
            var sf = await Package.Current.InstalledLocation.GetFileAsync(@"ContactXML.xml");
            XmlDocument xmlDoc;
            using (var stream = await sf.OpenAsync(FileAccessMode.ReadWrite))
            {
                xmlDoc = await XmlDocument.LoadFromFileAsync(sf);
                XmlElement root = xmlDoc.DocumentElement;
                IXmlNode xee = root.SelectSingleNode("//Contact/CGuid[.='" + c.CGuid + "']");
                xee.NextSibling.NextSibling.InnerText = c.Email;
                xee.NextSibling.InnerText = c.Name;
            }
            if (xmlDoc != null)
                await xmlDoc.SaveToFileAsync(sf);
        }

        public async void Delete(Contact c)
        {
            var sf = await Package.Current.InstalledLocation.GetFileAsync(@"ContactXML.xml");
            XmlDocument xmlDoc;
            using (var stream = await sf.OpenAsync(FileAccessMode.ReadWrite))
            {
                xmlDoc = await XmlDocument.LoadFromFileAsync(sf);
                XmlElement root = xmlDoc.DocumentElement;
                //IXmlNode xee = root.SelectSingleNode("//Contact/Name[.='" + c.Name + "'] | //Contact/Email[.='" + c.Email + "']");
                IXmlNode xee = root.SelectSingleNode("//Contact/CGuid[.='" + c.CGuid + "']");
                xee.ParentNode.RemoveChild(xee.NextSibling.NextSibling);
                xee.ParentNode.RemoveChild(xee.NextSibling);
                xee.ParentNode.RemoveChild(xee);

                IXmlNode clup = root.SelectSingleNode("//*[not(node())]");
                clup.ParentNode.RemoveChild(clup);
            }
            if (xmlDoc != null)
                await xmlDoc.SaveToFileAsync(sf);
        }
    }
}