How to implement the INotifyCollectionChanged interface?

Question

I assign a List<int> to the ItemsSource of ListBox, and the form inherits the INotifyCollectionChanged interface. However, when I delete the value in the List<int>, the CollectionChanged event will be null. How can I implement this interface?

my code example:

... 
private List<int> myin = new List<int>();

        public event NotifyCollectionChangedEventHandler CollectionChanged;

        //Remove a number.
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            myin.Remove(34);
            if (CollectionChanged != null) CollectionChanged(this,
                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove,myin));
        }

        //initalize List<int> and binding to ListBox.ItemsSource.
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            for(int i = 0; i < 100; i++)
            {
                myin.Add(i);
            }
            lis.ItemsSource = myin;
        }

Answer 1

Please use ObservableCollection to replace List, WPF provides the ObservableCollection<T> class, which is a built-in implementation of a data collection that implements the INotifyCollectionChanged interface.
Please update your myin and Button_Click as :

 ObservableCollection<int> myin = new ObservableCollection<int>();  
        private void Button_Click(object sender, RoutedEventArgs e)  
        {  
            myin.Remove(34);  
        }  

Then your demo will work like below:

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