Csharp/CSharp Tutorial/delegate/Multi cast delegate

Demonstrate multicasting

Create an invocation list, or chain, of methods that will be called when a delegate is invoked.

<source lang="csharp">using System;

delegate string StrMod(ref string str);

class MultiCastDemo {

 static string replaceSpaces(ref string a) { 
   Console.WriteLine("replaceSpaces"); 
   return a; 
 }  

 static string removeSpaces(ref string a) { 
   Console.WriteLine("removeSpaces"); 
   return a; 
 }  

 static string reverse(ref string a) { 
   Console.WriteLine("reverseSpaces"); 
   return a; 
 } 
    
 public static void Main() {  
   StrMod strOp; 
   StrMod replaceSp = new StrMod(replaceSpaces); 
   StrMod removeSp = new StrMod(removeSpaces); 
   StrMod reverseStr = new StrMod(reverse); 
   string str = "This is a test"; 

   // Set up multicast. 
   strOp = replaceSp; 
   strOp += reverseStr; 

   // Call multicast. 
   strOp(ref str); 
    
   // Remove replace and add remove. 
   strOp -= replaceSp; 
   strOp += removeSp; 

   str = "This is a test."; // reset string 

   // Call multicast. 
   strOp(ref str); 
 } 

}</source>

replaceSpaces
reverseSpaces
reverseSpaces
removeSpaces

Multicast delegates

<source lang="csharp">using System; class MainClass {

 delegate int MyDelegate(string s);
 static void Main(string[] args)
 {
   string MyString = "Hello World";
   
   MyDelegate Multicast = null;
   Multicast += new MyDelegate(DoSomething);
   Multicast += new MyDelegate(DoSomething2);
   Multicast(MyString);
 }
 static int DoSomething(string s)
 {
   Console.WriteLine("DoSomething");
   
   return 0;
 }
 static int DoSomething2(string s)
 {
     Console.WriteLine("DoSomething2");
   return 0;
 }

}</source>

DoSomething
DoSomething2

Remove delegate from Multicast

<source lang="csharp">using System; class MainClass {

 delegate int MyDelegate(string s);
 static void Main(string[] args)
 {
   string MyString = "Hello World";
   //Or you can Multicast delegates by doing this
   MyDelegate Multicast = null;
   Multicast += new MyDelegate(DoSomething);
   Multicast += new MyDelegate(DoSomething2);
   Multicast -= new MyDelegate(DoSomething2);

   Multicast(MyString);
 }
 static int DoSomething(string s)
 {
   Console.WriteLine("DoSomething");
   
   return 0;
 }
 static int DoSomething2(string s)
 {
     Console.WriteLine("DoSomething2");
   return 0;
 }

}</source>

DoSomething

uses the reference parameter of a multicast delegate as a counter

<source lang="csharp">using System; public delegate void DelegateClass(int valCount, ref int refCount); public class Counter {

   public static void Main() {
       DelegateClass del = (DelegateClass)AddOne + (DelegateClass)AddTwo + (DelegateClass)AddOne;
       int valCount = 0;
       int refCount = 0;
       del(valCount, ref refCount);
       Console.WriteLine("Value count = {0}", valCount); // 0
       Console.WriteLine("Reference count = {0}",refCount); // 4
   }
   public static void AddOne(int valCount,ref int refCount) {
       ++valCount;
       ++refCount;
   }
   public static void AddTwo(int valCount,ref int refCount) {
       valCount += 2;
       refCount += 2;
   }

}</source>