System.ComponentModel.PropertyDescriptor.AddValueChanged C# (CSharp) Method

        public virtual void AddValueChanged(object component, EventHandler handler)
        {
            if (component == null) throw new ArgumentNullException(nameof(component));
            if (handler == null) throw new ArgumentNullException(nameof(handler));

            if (_valueChangedHandlers == null)
            {
                _valueChangedHandlers = new Hashtable();
            }

            EventHandler h = (EventHandler)_valueChangedHandlers[component];
            _valueChangedHandlers[component] = Delegate.Combine(h, handler);
        }

 private EventMonitor(object instance, PropertyDescriptor property)
 {
     property.AddValueChanged(instance, (sender, e) =>
     {
         count++;
     });
 }