·a delegate
field can be marked as an event
wonly
+= and -= can be performed on
the field
wused widely
in GUI classes
namespace
System.Windows.Forms
{
public class Button : ...
{
...
public event EventHandler Click;
...
...
protected void OnClick(EventArgs e)
{
if (Click != null)
{
Click(this, e);
}
}
...
}
}