事件概述
事件的訂閱和取消訂閱
發布標准事件
引發派生類中的基類事件
BaseClassEvents
{
System;
System.Collections.Generic;
ShapeEventArgs : EventArgs
{
newArea;
ShapeEventArgs( d)
{
newArea = d;
}
NewArea
{
{ newArea; }
}
}
Shape
{
area;
Area
{
{ area; }
{ area = value; }
}
EventHandler<ShapeEventArgs> ShapeChanged;
Draw();
OnShapeChanged(ShapeEventArgs e)
{
EventHandler<ShapeEventArgs> handler = ShapeChanged;
(handler != )
{
handler(, e);
}
}
}
Circle : Shape
{
radius;
Circle( d)
{
radius = d;
area = 3.14 * radius;
}
Update( d)
{
radius = d;
area = 3.14 * radius;
OnShapeChanged( ShapeEventArgs(area));
}
OnShapeChanged(ShapeEventArgs e)
{
.OnShapeChanged(e);
}
Draw()
{
Console.WriteLine();
}
}
Rectangle : Shape
{
length;
width;
Rectangle( length, width)
{
.length = length;
.width = width;
area = length * width;
}
Update( length, width)
{
.length = length;
.width = width;
area = length * width;
OnShapeChanged( ShapeEventArgs(area));
}
OnShapeChanged(ShapeEventArgs e)
{
.OnShapeChanged(e);
}
Draw()
{
Console.WriteLine();
}
}
ShapeContainer
{
List<Shape> _list;
ShapeContainer()
{
_list = List<Shape>();
}
AddShape(Shape s)
{
_list.Add(s);
s.ShapeChanged += HandleShapeChanged;
}
HandleShapeChanged( sender, ShapeEventArgs e)
{
Shape s = (Shape)sender;
Console.WriteLine(, e.NewArea);
s.Draw();
}
}
Test
{
Main([] args)
{
Circle c1 = Circle(54);
Rectangle r1 = Rectangle(12, 9);
ShapeContainer sc = ShapeContainer();
sc.AddShape(c1);
sc.AddShape(r1);
c1.Update(57);
r1.Update(7, 7);
Console.WriteLine();
Console.WriteLine();
Console.ReadLine();
}
}
}
實現接口事件
WrapTwoInterfaceEvents
{
System;
IDrawingObject
{
EventHandler OnDraw;
}
IShape
{
EventHandler OnDraw;
}
Shape : IDrawingObject, IShape
{
EventHandler PreDrawEvent;
EventHandler PostDrawEvent;
EventHandler IDrawingObject.OnDraw
{
add { PreDrawEvent += value; }
remove { PreDrawEvent -= value; }
}
EventHandler IShape.OnDraw
{
add { PostDrawEvent += value; }
remove { PostDrawEvent -= value; }
}
Draw()
{
EventHandler handler = PreDrawEvent;
(handler != )
{
handler(, EventArgs());
}
Console.WriteLine();
handler = PostDrawEvent;
(handler != )
{
handler(, EventArgs());
}
}
}
Subscriber1
{
Subscriber1(Shape shape)
{
IDrawingObject d = (IDrawingObject)shape;
d.OnDraw += EventHandler(d_OnDraw);
}
d_OnDraw( sender, EventArgs e)
{
Console.WriteLine();
}
}
Subscriber2
{
Subscriber2(Shape shape)
{
IShape d = (IShape)shape;
d.OnDraw += EventHandler(d_OnDraw);
}
d_OnDraw( sender, EventArgs e)
{
Console.WriteLine();
}
}
Program
{
Main([] args)
{
Shape shape = Shape();
Subscriber1 sub = Subscriber1(shape);
Subscriber2 sub2 = Subscriber2(shape);
shape.Draw();
Console.WriteLine();
Console.ReadLine();
}
}
}
使用字典存儲事件實例
EventHandler1( i);
EventHandler2( s);
PropertyEventsSample
{
System.Collections.Generic.Dictionary<, System.Delegate> eventTable;
PropertyEventsSample()
{
eventTable = System.Collections.Generic.Dictionary<, System.Delegate>();
eventTable.Add(, );
eventTable.Add(, );
}
EventHandler1 Event1
{
add
{
eventTable[] = (EventHandler1)eventTable[] + value;
}
remove
{
eventTable[] = (EventHandler1)eventTable[] - value;
}
}
EventHandler2 Event2
{
add
{
eventTable[] = (EventHandler2)eventTable[] + value;
}
remove
{
eventTable[] = (EventHandler2)eventTable[] - value;
}
}
RaiseEvent1( i)
{
EventHandler1 handler1;
( != (handler1 = (EventHandler1)eventTable[]))
{
handler1(i);
}
}
RaiseEvent2( s)
{
EventHandler2 handler2;
( != (handler2 = (EventHandler2)eventTable[]))
{
handler2(s);
}
}
}
TestClass
{
Delegate1Method( i)
{
System.Console.WriteLine(i);
}
Delegate2Method( s)
{
System.Console.WriteLine(s);
}
Main()
{
PropertyEventsSample p = PropertyEventsSample();
p.Event1 += EventHandler1(TestClass.Delegate1Method);
p.Event1 += EventHandler1(TestClass.Delegate1Method);
p.Event1 -= EventHandler1(TestClass.Delegate1Method);
p.RaiseEvent1(2);
p.Event2 += EventHandler2(TestClass.Delegate2Method);
p.Event2 += EventHandler2(TestClass.Delegate2Method);
p.Event2 -= EventHandler2(TestClass.Delegate2Method);
p.RaiseEvent2();
}
}
事件的異步模式
