tests/ctags/events.cs

   1 // events1.cs
   2 using System;
   3 namespace MyCollections
   4 {
   5    using System.Collections;
   6
   7    // A delegate type for hooking up change notifications.
   8    public delegate void ChangedEventHandler(object sender, EventArgs e);
   9
  10    // A class that works just like ArrayList, but sends event
  11    // notifications whenever the list changes.
  12    public class ListWithChangedEvent: ArrayList
  13    {
  14       // An event that clients can use to be notified whenever the
  15       // elements of the list change.
  16       public event ChangedEventHandler Changed;
  17
  18       // Invoke the Changed event; called whenever list changes
  19       protected virtual void OnChanged(EventArgs e)
  20       {
  21          if (Changed != null)
  22             Changed(this, e);
  23       }
  24
  25       // Override some of the methods that can change the list;
  26       // invoke event after each
  27       public override int Add(object value)
  28       {
  29          int i = base.Add(value);
  30          OnChanged(EventArgs.Empty);
  31          return i;
  32       }
  33
  34       public override void Clear()
  35       {
  36          base.Clear();
  37          OnChanged(EventArgs.Empty);
  38       }
  39
  40       public override object this[int index]
  41       {
  42          set
  43          {
  44             base[index] = value;
  45             OnChanged(EventArgs.Empty);
  46          }
  47       }
  48    }
  49 }
  50
  51 namespace TestEvents
  52 {
  53    using MyCollections;
  54
  55    class EventListener
  56    {
  57       private ListWithChangedEvent List;
  58
  59       public EventListener(ListWithChangedEvent list)
  60       {
  61          List = list;
  62          // Add "ListChanged" to the Changed event on "List".
  63          List.Changed += new ChangedEventHandler(ListChanged);
  64       }
  65
  66       // This will be called whenever the list changes.
  67       private void ListChanged(object sender, EventArgs e)
  68       {
  69          Console.WriteLine("This is called when the event fires.");
  70       }
  71
  72       public void Detach()
  73       {
  74          // Detach the event and delete the list
  75          List.Changed -= new ChangedEventHandler(ListChanged);
  76          List = null;
  77       }
  78    }
  79
  80    class Test
  81    {
  82       // Test the ListWithChangedEvent class.
  83       public static void Main()
  84       {
  85       // Create a new list.
  86       ListWithChangedEvent list = new ListWithChangedEvent();
  87
  88       // Create a class that listens to the list's change event.
  89       EventListener listener = new EventListener(list);
  90
  91       // Add and remove items from the list.
  92       list.Add("item 1");
  93       list.Clear();
  94       listener.Detach();
  95       }
  96    }
  97 }
  98
  99 // events2.cs
 100 using System;
 101 namespace MyCollections
 102 {
 103    using System.Collections;
 104
 105    // A class that works just like ArrayList, but sends event
 106    // notifications whenever the list changes:
 107    public class ListWithChangedEvent: ArrayList
 108    {
 109       // An event that clients can use to be notified whenever the
 110       // elements of the list change:
 111       public event EventHandler Changed;
 112
 113       // Invoke the Changed event; called whenever list changes:
 114       protected virtual void OnChanged(EventArgs e)
 115       {
 116          if (Changed != null)
 117             Changed(this,e);
 118       }
 119
 120       // Override some of the methods that can change the list;
 121       // invoke event after each:
 122       public override int Add(object value)
 123       {
 124          int i = base.Add(value);
 125          OnChanged(EventArgs.Empty);
 126          return i;
 127       }
 128
 129       public override void Clear()
 130       {
 131          base.Clear();
 132          OnChanged(EventArgs.Empty);
 133       }
 134
 135       public override object this[int index]
 136       {
 137          set
 138          {
 139             base[index] = value;
 140             OnChanged(EventArgs.Empty);
 141          }
 142       }
 143    }
 144 }
 145
 146 namespace TestEvents
 147 {
 148    using MyCollections;
 149
 150    class EventListener
 151    {
 152       private ListWithChangedEvent List;
 153
 154       public EventListener(ListWithChangedEvent list)
 155       {
 156          List = list;
 157          // Add "ListChanged" to the Changed event on "List":
 158          List.Changed += new EventHandler(ListChanged);
 159       }
 160
 161       // This will be called whenever the list changes:
 162       private void ListChanged(object sender, EventArgs e)
 163       {
 164          Console.WriteLine("This is called when the event fires.");
 165       }
 166
 167       public void Detach()
 168       {
 169          // Detach the event and delete the list:
 170          List.Changed -= new EventHandler(ListChanged);
 171          List = null;
 172       }
 173    }
 174
 175    class Test
 176    {
 177       // Test the ListWithChangedEvent class:
 178       public static void Main()
 179       {
 180       // Create a new list:
 181       ListWithChangedEvent list = new ListWithChangedEvent();
 182
 183       // Create a class that listens to the list's change event:
 184       EventListener listener = new EventListener(list);
 185
 186       // Add and remove items from the list:
 187       list.Add("item 1");
 188       list.Clear();
 189       listener.Detach();
 190       }
 191    }
 192 }