Build a Pandora clone with Silverlight 4

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.IO.IsolatedStorage;
using System.Text;
using System.Linq;
using System.Runtime.Serialization;
using System.Diagnostics.Contracts;

namespace JudahHimango.Chavah
{
    public static class LocalDataStore
    {
        const string clientIdFileName = "clientId";
        const string settingsFileName = "settings";
        
        public static Guid GetClientId()
        {
            var existing = GetExistingIdOrNull();
            return existing.HasValue ? existing.Value : CreateNewId();
        }

        public static LocalSettings GetSettings()
        {
            Contract.Ensures(Contract.Result<LocalSettings>() != null);
            try
            {
                return GetSettingsOrNull() ?? CreateSettings();
            }
            catch
            {
                return CreateSettings();
            }
        }

        private static Guid CreateNewId()
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                Contract.Assume(store != null);
                using (var newFile = store.CreateFile(clientIdFileName))
                {
                    Contract.Assume(newFile != null);
                    var id = Guid.NewGuid();
                    var idBytes = id.ToByteArray();
                    Contract.Assume(idBytes != null);
                    newFile.Write(idBytes, 0, idBytes.Length);
                    return id;
                }
            }
        }

        private static LocalSettings GetSettingsOrNull()
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                var settingsFilePath = store.GetFileNames(settingsFileName).FirstOrDefault();
                if (settingsFilePath != null)
                {
                    using (var settingsFile = store.OpenFile(settingsFilePath, System.IO.FileMode.Open))
                    {
                        var serializer = new DataContractSerializer(typeof(LocalSettings));
                        return (LocalSettings)serializer.ReadObject(settingsFile);
                    }
                }
            }
            return null;
        }

        private static LocalSettings CreateSettings()
        {
            Contract.Ensures(Contract.Result<LocalSettings>() != null);

            using (var store = GetLocalStore())
            using (var newFile = store.CreateFile(settingsFileName))
            {
                var settings = new LocalSettings();
                var serializer = new DataContractSerializer(typeof(LocalSettings));
                serializer.WriteObject(newFile, settings);
                return settings;
            }
        }

        private static IsolatedStorageFile GetLocalStore()
        {
            Contract.Ensures(Contract.Result<IsolatedStorageFile>() != null);

            var storage = IsolatedStorageFile.GetUserStoreForApplication();
            Contract.Assume(storage != null);
            return storage;
        }

        private static Guid? GetExistingIdOrNull()
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                var fileName = store.GetFileNames(clientIdFileName).FirstOrDefault();
                if (fileName != null)
                {
                    using (var file = store.OpenFile(fileName, System.IO.FileMode.Open))
                    {
                        var idBytes = new byte[16];
                        file.Read(idBytes, 0, 16);
                        return new Guid(idBytes);
                    }
                }
            }
            return null;
        }
                
        public static void SaveSettings(LocalSettings localSettings)
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            using (var file = store.OpenFile(settingsFileName, System.IO.FileMode.OpenOrCreate))
            {
                var serializer = new DataContractSerializer(typeof(LocalSettings));
                serializer.WriteObject(file, localSettings);
            }
        }
    }
}