Why should we actually use Dependency Properties? - silverlight-4.0

Question

This code doesn't work :-
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using SilverlightPlainWCF.CustomersServiceRef;
using System.Diagnostics;
using System.Collections.ObjectModel;
using System.ComponentModel;
namespace SilverlightPlainWCF
{
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
this.DataContext = Customers;
this.Loaded += new RoutedEventHandler(MainPage_Loaded);
}
public static readonly string CustomersPropertyName = "Customers";
// public DependencyProperty CustomersProperty = DependencyProperty.Register(CustomersPropertyName,typeof(ObservableCollection<Customer>)
// ,typeof(MainPage),new PropertyMetadata(null));
private ObservableCollection<Customer> customers;
public ObservableCollection<Customer> Customers
{
//get { return GetValue(CustomersProperty) as ObservableCollection<Customer>; }
//set
//{
// SetValue(CustomersProperty, value);
//}
get
{
return customers;
}
set
{
customers = value;
}
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
CustomersServiceClient objCustomersServiceClient = new CustomersServiceClient();
objCustomersServiceClient.GetAllCustomersCompleted += (s, res) =>
{
if (res.Error == null)
{
Customers = res.Result;
}
else
{
MessageBox.Show(res.Error.Message);
}
};
objCustomersServiceClient.GetAllCustomersAsync();
}
private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
// Do not load your data at design time.
// if (!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
// {
// //Load your data here and assign the result to the CollectionViewSource.
// System.Windows.Data.CollectionViewSource myCollectionViewSource = (System.Windows.Data.CollectionViewSource)this.Resources["Resource Key for CollectionViewSource"];
// myCollectionViewSource.Source = your data
// }
// Do not load your data at design time.
// if (!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
// {
// //Load your data here and assign the result to the CollectionViewSource.
// System.Windows.Data.CollectionViewSource myCollectionViewSource = (System.Windows.Data.CollectionViewSource)this.Resources["Resource Key for CollectionViewSource"];
// myCollectionViewSource.Source = your data
// }
}
private void LayoutRoot_MouseLeave(object sender, MouseEventArgs e)
{
}
private void customerDataGrid_RowEditEnded(object sender, DataGridRowEditEndedEventArgs e)
{
var Customer = Customers[e.Row.GetIndex()];
Debug.WriteLine(Customer);
}
private void customerDataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
}
}
}
Whereas if i just change the above property of Customers to this :-
public static readonly string CustomersPropertyName = "Customers";
public DependencyProperty CustomersProperty = DependencyProperty.Register(CustomersPropertyName,typeof(ObservableCollection<Customer>)
,typeof(MainPage),new PropertyMetadata(null));
private ObservableCollection<Customer> customers;
public ObservableCollection<Customer> Customers
{
get { return GetValue(CustomersProperty) as ObservableCollection<Customer>; }
set
{
SetValue(CustomersProperty, value);
}
}
it works. Why is it that only with DependencyProperty the grid gets populated? Please explain me in little detail. Also, do i have to compulsorily use ObservableCollection or even List is fine?

Answer 1

Short answer: Dependency properties are wrappers which know how to 'dispatch changes'.
See Dependency Properties Overview