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WPF: Implement Change Notification Using INotifyPropertyChanged Interface

  • Article

Introduction

INotifyPropertyChanged was introduced in .NET 2.0. This interface has only one member, the PropertyChanged event that will notify listeners when a property of the implementing class is changed.

Demo

  • Open Visual Studio and select WPF application.
  • Open/add one user control or window.
  • Create one normal property FirstName as in the following:
private string  firstname = string.Empty;  
   
        public string  FristName  
        {  
            get { return firstname; }  
            set 
            {  
                firstname = value;  
              
            }  
 }
  • Add the same property into two controls as in the following:
<TextBlock Margin="2">First Name</TextBlock>  
<TextBox Margin="2" Grid.Row="0" Grid.Column="1" MinWidth="120" Text="{Binding Path=FristName,ElementName=ThisControl,UpdateSourceTrigger=PropertyChanged}"></TextBox>  
<TextBlock Margin="2" Grid.Column="2" Text="{Binding Path=FristName,ElementName=ThisControl,UpdateSourceTrigger=PropertyChanged}"></TextBlock>
  • Run the application, enter the first name field, but not displaying in my TextBlock in the right side.

http://www.c-sharpcorner.com/UploadFile/91c28d/implement-change-notification-using-inotifypropertychanged-i/Images/first%20name.jpg
http://www.c-sharpcorner.com/UploadFile/91c28d/implement-change-notification-using-inotifypropertychanged-i/Images/first.jpg

  • We can see the property change in the preceding picture. But it's not reflecting in the UI. 
  • Implement the INotifyPropertyChanged interface, no change in the XAML.
public partial  class INotify : UserControl, INotifyPropertyChanged  
   
 public INotify()  
 {  
     InitializeComponent();  
 }  
   
 private string  firstname = string.Empty;  
   
 public string  FristName  
 {  
     get { return firstname; }  
     set 
     {  
         firstname = value;  
         OnPropertyChanged("FristName");  
     }  
 }  
   
  
 #region INotifyPropertyChanged Members  
   
 public event  PropertyChangedEventHandler PropertyChanged;  
 public void  OnPropertyChanged(string txt)  
 {  
   
     PropertyChangedEventHandler handle = PropertyChanged;  
     if (handle != null)  
     {  
         handle(this, new  PropertyChangedEventArgs(txt));  
     }  
 }  
 #endregion
  • Run the application and see the change.

http://www.c-sharpcorner.com/UploadFile/91c28d/implement-change-notification-using-inotifypropertychanged-i/Images/new.jpg

  • We got the change in the UI.

Conclusion

The INotifyPropertyChanged interface will notify the source of changes to the target.

See Also