wpf - INotifyPropertyChanged with derive class -

i have class:

public class myfileinfo : inotifypropertychanged {     private string _file;     private int _bytessent;      public myfileinfo(string file)     {      }      public string file     {         { return _file; }         set { _file = value; }     }      public int bytessent     {         { return _bytessent; }         set { _bytessent= value; }     } } 

and derive class:

public class myfile : myfileinfo {  } 

so every time _bytessent has changed want notify:

public event propertychangedeventhandler propertychanged;  public virtual void notifypropertychange(string propertyname) {     var handler = propertychanged;     if (handler != null)         handler(this, new propertychangedeventargs(propertyname)); } 

using this:

public static int propertyname {     { return _propertyname; }     set     {         _totalpacketssent = value;         notifypropertychange("...");     } } 

so question is: should declare event ? in base class on 1 derive

by convention, should define in base class protected virtual name "oneventname":

protected virtual void onpropertychanged(string propertyname) {     var handler = propertychanged;     if (handler != null) handler(this, new propertychangedeventargs(propertyname)); }