WPF

public interface IBookDataService
{
    event EventHandler<HasChangesEventArgs> NotifyHasChanges;
    void Save(Action<SubmitOperation> submitCallback, object state);
    void GetBooksByCategory(
        Action<ObservableCollection<Book>> getBooksCallback,
        int categoryID,
        int pageSize);
    void GetCategories(Action<ObservableCollection<Category>> getCategoriesCallback);
}

public class BookDataService : IBookDataService
   {
       private LoadOperation<Book> _booksLoadOperation;
       private LoadOperation<Category> _categoriesLoadOperation;

       private Action<ObservableCollection<Book>> _getBooksCallback;
       private Action<ObservableCollection<Category>> _getCategoriesCallback;

       private int _pageIndex = 0;
       private BookClubContext Context { get; set; }
       public event EventHandler<HasChangesEventArgs> NotifyHasChanges;

       public BookDataService()
       {
           Context = new BookClubContext();
           Context.PropertyChanged += ContextPropertyChanged;
       }


       private void ContextPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
       {
           if (NotifyHasChanges != null)
           {
               NotifyHasChanges(this, new HasChangesEventArgs(){HasChanges  = Context.HasChanges});
           }
       }

       public void Save(Action<SubmitOperation> submitCallback, object state)
       {
           if (Context.HasChanges)
           {
               Context.SubmitChanges(submitCallback, state);
           }
       }

       public void GetBooksByCategory(
           Action<ObservableCollection<Book>> getBooksCallback,
           int categoryID,
           int pageSize)
       {
           ClearBooks();
           var query = Context.GetBooksByCategoryQuery(categoryID).Take(pageSize);
           RunBooksQuery(query, getBooksCallback);
       }

       public void GetBooksByTitle(Action<ObservableCollection<Book>> getBooksCallback, int categoryID, string titleFilter)
       {
           ClearBooks();
           var query = Context.GetBooksByCategoryQuery(categoryID)
               .Where(b => b.Title.Contains(titleFilter));
           RunBooksQuery(query, getBooksCallback);
       }

       private void ClearBooks()
       {
           _pageIndex = 0;
           Context.Books.Clear();
       }

       private void RunBooksQuery(EntityQuery<Book> query, Action<ObservableCollection<Book>> getBooksCallback)
       {
           _getBooksCallback = getBooksCallback;
           _booksLoadOperation = Context.Load<Book>(query);
           _booksLoadOperation.Completed += OnLoadBooksCompleted;
       }

       private void OnLoadBooksCompleted(object sender, EventArgs e)
       {
           _booksLoadOperation.Completed -= OnLoadBooksCompleted;
           var books = new EntityList<Book>(Context.Books, _booksLoadOperation.Entities);
           _getBooksCallback(books);
       }

       public void GetCategories(Action<ObservableCollection<Category>> getCategoriesCallback)
       {
           _getCategoriesCallback = getCategoriesCallback;
           Context.Categories.Clear();
           _categoriesLoadOperation = Context.Load<Category>(Context.GetCategoriesQuery());
           _categoriesLoadOperation.Completed += OnLoadCategoriesCompleted;
       }

       private void OnLoadCategoriesCompleted(object sender, EventArgs e)
       {
           _categoriesLoadOperation.Completed -= OnLoadCategoriesCompleted;
           var categories = new EntityList<Category>(Context.Categories, _categoriesLoadOperation.Entities);
           _getCategoriesCallback(categories);
       }
   }

 public void LoadBooksByCategory()
 {
     //Books.Clear();
     Books = null;
     if (SelectedCategory != null)
         BookDataService.GetBooksByCategory(GetBooksCallback, SelectedCategory.CategoryID, _pageSize);
 }

private void GetBooksCallback(ObservableCollection<Book> books)
 {
     if (books != null)
     {
         if (Books == null)
         {
             Books = books;
         }
         else
         {
             foreach (var book in books)
             {
                 Books.Add(book);
             }
         }

         if (Books.Count > 0)
         {
             SelectedBook = Books[0];
         }

     }
 }

public class State
{
	public State()
	{
		Counties = new ObservableCollection<County>();
	}

	public String StateName
	{ get; set; }

	public String NickName
	{ get; set; }

	public ObservableCollection<County> Counties
	{ get; set; }
}

public class County
{
	public County()
	{
	}

	public String CountyName
	{ get; set; }

	public String Population
	{ get; set; }
}

<ListView ItemsSource="{Binding}"> 
        <ListView.View>
             <GridView>
                    <GridViewColumn Header=" State Name " DisplayMemberBinding="{Binding StateName}" />
                    <GridViewColumn Header=" County Name" DisplayMemberBinding="{Binding Counties.CountyName}" />
                    <GridViewColumn Header=" Population " DisplayMemberBinding="{Binding Counties.Population}"/>
             </GridView>
        </ListView.View>
</ListView>

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            DataTable _dtPayments = GetPayments(_intID);
                DataView defaultView = _dtPayments.DefaultView;

                dgPayments.ItemsSource = defaultView;
        }

public class clsPaymentViewModel : INotifyPropertyChanged
    {
        clsPaymentManager _PaymentManager = new clsPaymentManager();

        public clsPaymentViewModel(int intID)
        {
            DataCollection = _PaymentManager.GetPayments(intID);
        }

        #region INotifyPropertyChanged
        public event PropertyChangedEventHandler PropertyChanged;

        protected void RaisePropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
        #endregion

        private ObservableCollection<clsPayment> mDataCollection;

        public ObservableCollection<clsPayment> DataCollection
        {
            get { return mDataCollection; }
            set
            {
                mDataCollection = value;
                RaisePropertyChanged("DataCollection");
            }
        }

    }
/////////////////////////////////////////////////////////
    {
        public ObservableCollection<clsPayment> GetPayments(int intID)
        {
            ObservableCollection<clsPayment> ret;

            List<clsPayment> payments = GetPaymentsCol(intID);

            ret = new ObservableCollection<clsPayment>(payments);
            return ret;
        }

    }

clsPaymentViewModel _ViewModel;

public frmPayment()
        {
            InitializeComponent();

            int _intID = 1
            _ViewModel = new clsPaymentViewModel(_intID);
        }