C#

Jacek Gajek wrote:

I think I don't exactly understand how all this works.

Mark Nischalke wrote:

Exactly.

IMO trying to make a generic method such as you are trying is fruitless and unnecessary. Don't you think Microsoft would have implemented such method already if it was such a good idea?

EventManager.RegisterClassHandler(typeof(ListBox), KeyDownEvent, new KeyEventHandler(ListBox_KeyDown));

private static void ListBox_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Delete)
    {
        var listBox = sender as ListBox;
        if (listBox != null)
        {
            object item = listBox.SelectedItem;
            if (item != null)
            {
                var list = listBox.ItemsSource as IList;
                if (list != null)
                    list.Remove(item);
            }
        }
    }
}

class ObservableTable<T> : ObservableCollection<T> where T : class
{
    private readonly ObjectQuery<T> _table;
    private readonly ObjectContext _context;
    public ObservableTable(ObjectQuery<T> table, ObjectContext context) : base(table)
    {
        _table = table;
        _context = context;
    }

    public ObjectQuery<T> Table
    {
        get { return _table; }
    }

    protected override void InsertItem(int index, T item)
    {
        base.InsertItem(index, item);

        _context.AddObject(typeof(T).Name, item);
    }
    protected override void RemoveItem(int index)
    {
        T item = this[index];
        base.RemoveItem(index);
        _context.DeleteObject(item);        
    }
}

try
{
  // blah blah
}
catch (InvalidOperationException e1)
{
  // do something
}
catch (ThisOtherException e2)
{
}
catch (Exception e3)
{
   // this is where you handle any exception not already caught.
}

Binary   Hex  byte sbyte
00000000 0x00    0     0
...
01111111 0x7F  127   127
10000000 0x80  128  -128
...
11111111 0xFF  255  -  1

10000000 0x80  128  -127

if (value) {
    emit('-');
    value = -value;   // <<<<<<<<<
}
// now process positive number