. NET delegate

Delegate Type Definition

 

• Delegated instance

When to use delegation instead of using interfaces

• Use delegation in the following cases

• Use the interface in the following cases

• Delegate Declaration

ProcessBookDelegate(Book book);

• Instantiate Delegation

• Call delegate

• Multi-channel broadcast Delegation

 

Del( s); TestClass{ Hello( s) { System.Console.WriteLine(, s); } Goodbye( s) { System.Console.WriteLine(, s); } Main() { Del a, b, c, d; a = Hello; b = Goodbye; c = a + b; d = c - a; System.Console.WriteLine(); a(); System.Console.WriteLine(); b(); System.Console.WriteLine(); c(); System.Console.WriteLine(); d(); }}

Anonymous Method

 

(System.Object o, System.EventArgs e) { System.Windows.Forms.MessageBox.Show(); }; Del( x);Del d = ( k) { }; StartThread(){ System.Threading.Thread t1 = System.Threading.Thread (() { System.Console.Write(); System.Console.WriteLine(); }); t1.Start();}

• Co-Variation and inverter in Delegation

Mammals{} Dogs : Mammals{} Program{ Mammals HandlerMethod(); Mammals FirstHandler(){ ;} Dogs SecondHandler(){ ;} Main() { HandlerMethod handler1 = FirstHandler; HandlerMethod handler2 = SecondHandler; }}

Form1(){ InitializeComponent(); lastActivity = System.DateTime(); .textBox1.KeyDown += .MultiHandler; .button1.MouseClick += .MultiHandler; } MultiHandler( sender, System.EventArgs e){ lastActivity = System.DateTime.Now;}

• Generic Delegation

Del<T>(T item); Notify( i) { }Del<> m1 = Del<>(Notify);

• Method group Conversion

> m2 = Notify;

• Generic class internal definition delegate use of generic class type parameters

Stack<T>{ T[] items; index; StackDelegate(T[] items);}

• The code that references the delegate must specify the type variable containing the class

DoWork([] items) { } TestStack(){ Stack<> s = Stack<>(); Stack<>.StackDelegate d = DoWork;}

• Generic delegation replaces traditional binning Delegation

StackEventHandler<T, U>(T sender, U eventArgs); Stack<T>{ StackEventArgs : System.EventArgs { } StackEventHandler<Stack<T>, StackEventArgs> stackEvent; OnStackChanged(StackEventArgs a) { stackEvent(, a); }} SampleClass{ HandleStackChange<T>(Stack<T> stack, Stack<T>.StackEventArgs args) { }} Test(){ Stack<> s = Stack<>(); SampleClass o = SampleClass(); s.stackEvent += o.HandleStackChange;}