C # delegates and events

A delegate is a chain of methods that allows an object to execute the method on the chain in turn. Can simplify code and improve efficiency. Statement

public delegate int delegate (int i);//Declaration Delegate

Matching rules for delegate registration methods: The method amount return type must be the same as the return type of the delegate. The parameter of the method must be the same as the delegate's method parameter, and the parameter name can be different.

public void F1 (int i,int j);//nopublic int F2 (int i);//nopublic int F3 (int m,int n);//yes

Instantiating a delegate delegate is a class, so you need to instantiate it.

namespace Test{delegate int delegate (int i), class program{public int F1 (int i) {return i;} static void Main (string[] args) {program P=new program ();D elegate d1=new Delegate (P.F1);//Create Instance}}}

A delegate's method list binds multiple methods to the same delegate variable. , you can call all bound methods at one time when the delegate variable is called.

namespace Test{delegate int delegate (int i), class Program<pre Name= "code" class= "CSharp" >namespace test{public delegate int delegate (int i);p ublic class program{public static int F1 (int i) {return i;} public int F2 (int j) {return J;} static void Main (string[] args) {program P=new program ();D elegate d1=new Delegate (p.f1);D elegate d2=new Delegate (P.F2);D Elegate d3=d1+d2;//to delegate registration method int I3=D3 (10);}}

Calling a delegate delegate is a method chain that invokes a delegate that invokes all the methods contained by the delegate instance.

namespace Test{public delegate void delegate (int i);p ublic class program{public static void F1 (int i) {Console.WriteLine (i . ToString ());} public static void F2 (int i) {cosnole.writeline (i.tostring ());} static void Main (string[[] args) {Delegate d1=new Delegate (program.f1);D elegate d2=new Delegate (PROGRAM.F2);D elegate D3 =D1+D2;D1 (10);//Call D1 Instance D2 (200);//Call D2 instance D3 (201);//Call D3 instance}}}

An event event is a special delegate that declares an event

public delegate void EventHandler (Object Sender,eventargs e);

Declaring the event itself

Public event EventHandler print;//Declaration event Print

Registering Events & removing events

namespace Test{public delegate void EventHandler (Object Sender,eventargs E) class Program{public event EventHandler Print ;p ublic void F1 (Object Sender,eventargs e) {Console.WriteLine ("F1");} public void F2 (Object Sender,eventargs e) {Console.WriteLine ("F2");} static void Main (string[] args) {program P=new program ();p. Print+=new EventHandler (P.F1);//Register a method p for the event. Print+=new EventHandler (P.F2); if (p.print!=null) {p.print (null,null);} Console.WriteLine ();p. Print-=new EventHandler (P.F1);//Remove the method from the event f1;if (p.print!=null) {p.print (null,null);} Console.ReadLine ();}}}

Invoke Event

namespace Test{public delegate void EventHandler (Object Sender,eventargs e); class Program{public Event EventHandler print;public void F1 (Object Sender,eventargs e) {Console.WriteLine ("F1");} static void Main (string[] args) {program P=new program ();p. Print+=new EventHandler (P.F1); if (p.print!=null) {P.print ( Null,null);//Call Event}console.readline ();}}}

C # delegates and events