InotifyPropertyChanged implementing Error

Question

'ContactManager.Notifier' does not implement interface member 'System.ComponentModel.INotifyPropertyChanged.PropertyChanged' C:\Users\1352756\AppData\Local\Temporary Projects\ContactManager\Notifier.cs 7 27 ContactManager

 

This is the Error i am getting and i can not find any solution for this.......

 

namespace ContactManager

{

[Serializable]

public abstract class Notifier:INotifyPropertyChanged

{

[field: NonSerialized]

public event PropertyChangedEventHandler propertychanged;

protected virtual void Onpropertychanged(string propertyname)

{

var Eventhandler = this.propertychanged;

Onpropertychanged("propertyname");

if (Eventhandler != null)

{

Eventhandler(this,

new PropertyChangedEventArgs(propertyname)

);

}

}

}

}

 

Please Help!