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 automatically, and your GUI should now update whenever you set your class invokes the PropertyChanged event handler.

[Edit to add:] Additionally, the BindingList class expose 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()); }