Question

I have a DataGridView and a BindingSource bs populated using bs.DataSource = list; where list is a BindingList<Item>.

All I want is to have each changed Item notified that it is changed, and each deleted item notified that it is deleted. Or instead, I would like to have access to changed, new and deleted items after user edits the grid and presses the button.

Edit:

public abstract class Item : INotifyPropertyChanged { .......
public Item()
{
    Id = IdCounter++;
    Pairs = new HashSet<int>();
    State = ItemState.NEW;
    Name = "#noname";
    Note = "";
    PropertyChanged += new PropertyChangedEventHandler(Item_PropertyChanged);
}

void Item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    SetChanged();
}

/* nastaví příznak, že se něco změnilo - to následně vyvolá UPDATE (při použití SQL úložiště) */
public void SetChanged()
{
    State = ItemState.CHANGED;
}

Answer 1

Youll want to listen for the ListChanged event on your BindingList<Item> or BindingSource bs. In the ListChangedEventArgs, the ListChangedType with have specific details about what changed:

Reset – Much of the list has changed. Any listening controls should
refresh all their data from the list.

ItemAdded – An item added to the
list. NewIndex contains the index of the item that was added.

ItemDeleted – An item deleted from the list. NewIndex contains the
index of the item that was deleted.

ItemMoved – An item moved within
the list. OldIndex contains the previous index for the item, whereas
NewIndex contains the new index for the item.

ItemChanged – An item
changed in the list. NewIndex contains the index of the item that was
changed.

I bolded the ones you mentioned.

Update

Ok, so this is what the Item class should look like:

public class Item : INotifyPropertyChanged
{
   public event PropertyChangedEventHandler PropertyChanged;

   private int _Id;
   private HashSet<int> _Pairs;
   private ItemState _State;
   private String _ItemName;
   private String _Note;

   public Item()
   {
      Id = IdCounter++;
      Pairs = new HashSet<int>();
      State = ItemState.NEW;
      Name = "#noname";
      Note = "";      
   }

   public int Id
   {
      get { return _Id; }
      set
      {
         if(_Id != value)
         {
            _Id = value;
            NotifyPropertyChanged("Id");
         }
      }
   }

   ... Implement other properties like above/below

   // Dont use 'Name' as a property type
   public String ItemName
   {
      get { return _ItemName; }
      set
      {
         if(_ItemName!= value)
         {
            _ItemName= value;
            NotifyPropertyChanged("ItemName");
         }
      }
   }

   ...

   public void NotifyPropertyChanged(String propertyName)
   {
      PropertyChangedEventHandler prop_changed = PropertyChanged;
      if (prop_changed != null)
      {
         prop_changed(this, new PropertyChangedEventArgs(propertyName));
      }
   }
}

Then when you attach to you BindingList you should get the updates. Then you can change the state of your item when you receive those events or through databinding.