MVVM for Multi Platforms

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.ComponentModel;

using GeographicRepresentation.Interfaces;
using GeographicRepresentation.Lib;

namespace GeographicRepresentation.UILib.View
{
    /// <summary>
    /// Interaction logic for ContinentsViewGrid.xaml
    /// </summary>
    public partial class ContinentsViewGrid : Grid, INotifyPropertyChanged
    {
        #region Members

        IReadOnlyViewModel m_SelectedObject;        

        #endregion

        #region Properties

        public IReadOnlyViewModel SelectedObject
        {
            get { return m_SelectedObject; }
            set
            {
                m_SelectedObject = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("SelectedObject"));
                }
            }
        }        

        #endregion

        #region Methods

        #region Ctor

        public ContinentsViewGrid()
        {
            InitializeComponent();
            m_SelectedObject = null;
        }

        #endregion

        private void Grid_Loaded(object sender, RoutedEventArgs e)
        {
            IContinentsListViewModel vm = InterfacesFactory.Instance.GetContinentsListViewModel();
            this.DataContext = vm;
            SelectedObject = vm.Continents[0];
            
        }

        private void continentsView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {            
            // When the selected item changes, unregister the changed event
            UnregisterChangedDataEvent();
            SelectedObject = e.NewValue as IReadOnlyViewModel;
            // Register the new selected object to a changed data event
            RegisterChangedDataEvent();            
        }

        private void UnregisterChangedDataEvent()
        {
            if (m_SelectedObject != null)
            {
                Type[] types = m_SelectedObject.GetType().GetInterfaces();                
                
                if (types.Contains(typeof(IReadOnlyContinentViewModel)))
                {
                    IReadOnlyContinentViewModel vm = m_SelectedObject as IReadOnlyContinentViewModel;
                    vm.OnBestCityToBeInChanged -= this.DataChanged;
                }
                else if (types.Contains(typeof(IReadonlyCountryViewModel)))
                {
                    IReadonlyCountryViewModel vm = m_SelectedObject as IReadonlyCountryViewModel;
                    vm.OnBirthRateChanged -= this.DataChanged;
                }
            }
        }

        private void RegisterChangedDataEvent()
        {
            if (m_SelectedObject != null)
            {
                Type[] types = m_SelectedObject.GetType().GetInterfaces();                

                if (types.Contains(typeof(IReadOnlyContinentViewModel)))
                {
                    IReadOnlyContinentViewModel vm = m_SelectedObject as IReadOnlyContinentViewModel;
                    vm.OnBestCityToBeInChanged += this.DataChanged;
                }
                else if (types.Contains(typeof(IReadonlyCountryViewModel)))
                {
                    IReadonlyCountryViewModel vm = m_SelectedObject as IReadonlyCountryViewModel;
                    vm.OnBirthRateChanged += this.DataChanged;
                }                
            }
        }

        /// <summary>
        /// A Change in the data would carry data update
        /// </summary>
        private void DataChanged()
        {
            SelectedObject = m_SelectedObject;            
        }                

        /// <summary>
        /// Call for updating the data. This set an asynchronos call for the view model
        /// </summary>
        public void UpdateData()
        {
            IContinentsListViewModel vm = this.DataContext as IContinentsListViewModel;
            SimpleOperationDelegate delg = new SimpleOperationDelegate(vm.LoadContinentsFromRepository);
            delg.BeginInvoke(this.UpdateDataCompleted, delg);
        }

        /// <summary>
        /// Call back for the data reloading. The update should take place in the main thread
        /// </summary>
        /// <param name="result"></param>
        private void UpdateDataCompleted(IAsyncResult result)
        {
            System.Windows.Application.Current.Dispatcher.BeginInvoke(new AsyncCallback(this.UpdateDataCompletedInMainThread), result);
        }

        /// <summary>
        /// Update the view
        /// </summary>
        /// <param name="result"></param>
        private void UpdateDataCompletedInMainThread(IAsyncResult result)
        {
            if (result.IsCompleted)
            {
                continentsView.Items.Refresh();
                SimpleOperationDelegate delg = result.AsyncState as SimpleOperationDelegate;
                delg.EndInvoke(result);
            }
        }

       

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion  

        #endregion
        
    }    
}