How to capture old value and new value in INotifyPropertyChanged implementation of PropertyChanged event in C#

Question

I need to capture old value, new value and property name in PropertyChanged event handler. The default implementation of INotifyPropertyChanged provides only name of the pro

Answer 1

Just Implement your own PropertyChangedEventArgs.

Implemeting a new Interface not necessary.

This solutions works. Here is one of the benefits of polymorphism

public class PropertyChangedExtendedEventArgs : PropertyChangedEventArgs
{
        public virtual object OldValue { get; private set; }
        public virtual object NewValue { get; private set; }

        public PropertyChangedExtendedEventArgs(string propertyName, object oldValue, 
               object newValue)
               : base(propertyName)
        {
            OldValue = oldValue;
            NewValue = newValue;
        }
    }

public class NotifyObject : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void NotifyPropertyChanged(string propertyName, object oldvalue, object newvalue)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedExtendedEventArgs(propertyName, oldvalue, newvalue));
        }
    }



public class Person : NotifyObject
    {
        private int _name;
        public int Name
        {
            get { return _name; }
            set
            {
                var oldValue = _name;
                _name = value;
                NotifyPropertyChanged("Name", oldValue, value);

            }
        }
    }

And your view model

Person person = new Person();
person.PropertyChanged += person_PropertyChanged;

  void person_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            var args = e as PropertyChangedExtendedEventArgs;
            //do whatever you want
        }