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.Net List with Changed event

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Sometimes we need a List which can notify user when an item is added. Here is the way that you can implement a generic ArrayList which notifies user at the time of an element is added.

 

using System;

using System.Collections;

namespace ArchiveData.Logging

{

  // A delegate type for hooking up change notifications.

  public delegate void ChangedEventHandler(object sender, EventArgs e);

  public class ListWithChangedEvent : ArrayList

  {

    // An event that clients can use to be notified whenever the

    // elements of the list change.

    public event ChangedEventHandler Changed;

    public object NewlyAddedItem { get; set; }

    // Invoke the Changed event; called whenever list changes

    protected virtual void OnChanged(EventArgs e)

    {

      if (Changed != null)

        Changed(this, e);

    }

    // Override some of the methods that can change the list;

    // invoke event after each

    public override int Add(object value)

    {

      NewlyAddedItem = value;

      var i = base.Add(value);

      OnChanged(EventArgs.Empty);

      return i;

    }

    public override void Clear()

    {

      base.Clear();

      OnChanged(EventArgs.Empty);

    }

    public override object this[int index]

    {

      set

      {

        base[index] = value;

        OnChanged(EventArgs.Empty);

      }

    }

  }

}

 

 

I got this from MSDN. I feel that it would be helpful to you all too.

 

Enjoy!

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