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Implementing INotifyPropertyChanged

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4.80/5 (14 votes)
17 Mar 2010CPOL1 min read
This article shows how to implement INotifyPropertyChanged.

Introduction

If an object implements the INotifyPropertyChanged interface, it’ll raise a property changed event when its property changes. Let's create a sample application to know how we can implement the INotifyPropertyChanged Interface. I am creating a Silverlight application which demonstrates data binding with both an object implementing INotifyPropertyChanged and also a normal DependencyProperty.

  • Open Visual Studio and select a new Silverlight application.
  • Create a class named Customer in the Silverlight project and implement INotifyPropertyChanged.
    C#
    public class Customer : INotifyPropertyChanged
    {
  • Define the INotifyPropertyChanged members:
    C#
    public event PropertyChangedEventHandler PropertyChanged;
    
    public void OnPropertyChanged(PropertyChangedEventArgs e)
    {
       if (PropertyChanged != null)
       {
          PropertyChanged(this, e);
       }
    }
  • In the property setter, invoke OnPropertyChanged by passing a property name like:
    C#
    private string _Name;
    
    public string Name
    {
      get
      {
         return _Name;
      }
      set
      {
         _Name = value;
         OnPropertyChanged(new PropertyChangedEventArgs("Name"));
      }
    }
  • In MainPage.xaml.cs, add an ObservableCollection of Customer objects as a Dependency Property in order to make sure that the UI is updating while we assigning the customer list to another list or object. If we are making it as a normal property, the UI will update only if we add a new object to the customer list or if any change occurs to the underlying properties.
    C#
    public ObservableCollection<Customer> CustomerList
    {
      get { return (ObservableCollection<Customer>)
           GetValue(CustomerListProperty); }
      set { SetValue(CustomerListProperty, value); }
    }
    
    // Using a DependencyProperty as the backing store for MyProperty.
    This enables animation, styling, binding, etc...
    public static readonly DependencyProperty CustomerListProperty =
    DependencyProperty.Register("CustomerList",
    typeof(ObservableCollection<Customer>), typeof(MainPage),
        new PropertyMetadata(new ObservableCollection<Customer>()));
  • I also added a DependencyProperty, FirstName, in MainPage.xaml.cs just to show the binding of a simple DependencyProperty.
    C#
    public string FirstName
    {
      get { return (string)GetValue(FirstNameProperty); }
      set { SetValue(FirstNameProperty, value); }
    }
    
    // Using a DependencyProperty as the backing store for MyProperty.
    This enables animation, styling, binding, etc...
    public static readonly DependencyProperty FirstNameProperty =
      DependencyProperty.Register("FirstName", typeof(string), typeof(MainPage),
      new PropertyMetadata(string.Empty)); 
  • In MainPage.XAML, add a DataGrid and TextBox and bind them to the ObservableCollection and DependencyProperty, respectively.
    XML
    <data:DataGrid AutoGenerateColumns="True"
       Width="400"
       Height="300"
       ItemsSource="{Binding ElementName=TestUC,
                                    Path=CustomerList}">
    </data:DataGrid>
    <TextBox x:Name="NameTextBox"
       Text="{Binding ElementName=TestUC, Path=FirstName, Mode=TwoWay}"
       Width="100"
       Height="25"
       Margin="0,10,0,10" />
  • For understanding the PropertyChanged event, I added a button and just updated the Customer object in the Click event so that you can see the changes in the DataGrid. When you change a property of the Customer object from the Click event, you can see that the UI is updating accordingly.
  • Download Sample application from Implementing INotifyPropertyChanged.
This article was originally posted at http://codepronet.blogspot.com/feeds/posts/full

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Software Developer Tata Consultancy Services
India India
I have been working in different .NET Technologies like ASP.NET,WPF,Silverlight for the last few years.I am enjoying my life as a Programmer and spending time with my Family,Friends & Camera.

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Comments and Discussions

 
GeneralSuggestion Pin
Richard Deeming25-Mar-10 8:16
mveRichard Deeming25-Mar-10 8:16 
GeneralGood article; small sidenote Pin
Andrei Ion Rînea8-Sep-09 1:46
Andrei Ion Rînea8-Sep-09 1:46 
GeneralRe: Good article; small sidenote Pin
Arun Jacob8-Sep-09 4:09
Arun Jacob8-Sep-09 4:09 
GeneralRe: Good article; small sidenote Pin
Andrei Ion Rînea8-Sep-09 6:14
Andrei Ion Rînea8-Sep-09 6:14 
GeneralRe: Good article; small sidenote Pin
Arun Jacob8-Sep-09 19:35
Arun Jacob8-Sep-09 19:35 

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