Cache System in Silverlight 5 RIA Application - Part 1 - Data Load

using System;
using System.ComponentModel;
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 PortableLibrary;
using PortableLibrary.Common;
using SilverlightClient.Common;
using SilverlightClient.Mapping;

namespace SilverlightClient.Core
{
    public class ModelManager
    {
        #region SINGLETON

        static ModelManager instance = null;
        static readonly object padlock = new object();

        public static ModelManager Instance
        {
            get
            {
                lock (padlock)
                {
                    if (instance == null)
                    {
                        instance = new ModelManager();
                    }
                    return instance;
                }
            }
        }

        #endregion SINGLETON

        private GlobalCache cache;

        private LoginService.LoginClient loginServiceClient;

        public ModelManager()
        {
            this.cache = new GlobalCache();

            this.loginServiceClient = new LoginService.LoginClient();
        }

        public void Load(BaseViewModel viewModelContext, String operation, Array parameters)
        {
            switch (operation)
            {
                case OperationType.LOAD_USER:
                    if (null != cache.LoadProperty(CacheMapping.USER_CONTEXT))
                    {
                        viewModelContext.WriteProperty(MainViewModelMapping.USER_CONTEXT, cache.LoadProperty(CacheMapping.USER_CONTEXT), typeof(UserContext));
                    }
                    else
                    {
                        LoadForce(viewModelContext, operation, parameters);
                    }
                    break;
            }
        }

        public void LoadForce(BaseViewModel viewModelContext, String operation, Array parameters)
        {
            switch (operation)
            {
                case OperationType.LOAD_USER:
                    UserLogin(viewModelContext, parameters);
                    break;
            }
        }

        private void UserLogin(BaseViewModel viewModelContext, Array parameters)
        {
            String username = parameters.GetValue(0) as String;

            String password = parameters.GetValue(1) as String;

            loginServiceClient.UserLoginCompleted += (sender, e) =>
            {
                var uc = e.Result as UserContext;

                cache.WriteProperty(CacheMapping.USER_CONTEXT, uc, typeof(UserContext));
                viewModelContext.WriteProperty(MainViewModelMapping.USER_CONTEXT, uc, typeof(UserContext));
            };

            loginServiceClient.UserLoginAsync(username, password);
        }
    }
}