How can I detect changes to item properties in the BindingList<T> ?

Question

I have a custom class Foo with properties A and B. I want to display it in a databinding control.

I have created a class Foos : BindingList<Foo> .

In order to update some internal properties of the Foos class I need to be notified of property changes (I can handle insertions, removals etc.) on the items in the list. How would you implement that functionality ?

Should I inherit Foo from some object in the framework that supports that ? I think I could create events that notify me if changes, but is that the way it should be done ? Or is there some pattern in the framework, that would help me ?

Answer 1

Foo should implement the INotifyPropertyChanged and INotifyPropertyChanging interfaces.

public void Foo : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    private int _someValue;
    public int SomeValue
    {
        get { return _someValue; }
        set { _someValue = value; NotifyPropertyChanged("SomeValue"); }
    }
}

The BindingList should hook onto your event handler automagically, and your GUI should now update whever you set your class invokes the PropertyChanged event handler.

[Edit to add:] Additionally, the BindingList class exposted two events which notify you when the collection has been added to or modified:

public void DoSomething()
{
    BindingList<Foo> foos = getBindingList();
    foos.ListChanged += HandleFooChanged;
}

void HandleFooChanged(object sender, ListChangedEventArgs e)
{
    MessageBox.Show(e.ListChangedType.ToString());
}