List firing Event on Change

Question

I created a Class EventList inheriting List which fires an Event each time something is Added, Inserted or Removed:

public          


        

Answer 1

If an ObservableCollection is not the solution for you, you can try that:

A) Implement a custom EventArgs that will contain the new Count attribute when an event will be fired.

public class ChangeListCountEventArgs : EventArgs
{
    public int NewCount
    {
        get;
        set;
    }

    public ChangeListCountEventArgs(int newCount)
    {
        NewCount = newCount;
    }
}

B) Implement a custom List that inherits from List and redefine the Count attribute and the constructors according to your needs:

public class CustomList : List
{
    public event EventHandler ListCountChanged;

    public new int Count
    {
        get
        {
            ListCountChanged?.Invoke(this, new ChangeListCountEventArgs(base.Count));
            return base.Count;
        }
    }

    public CustomList()
    { }

    public CustomList(List list) : base(list)
    { }

    public CustomList(CustomList list) : base(list)
    { }
}

C) Finally subscribe to your event:

var myList = new CustomList();
myList.ListCountChanged += (obj, e) => 
{
    // get the count thanks to e.NewCount
};