what is the purpose of delegates in C#

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So i just started studying C# and realised the actual necessity of C#.
Please provide me an example in C# such that the example demonstrates something which can be done by a delegate but cannot be done by a function call something like the following

public void ReplicateDeligate(int x,int y)
   {
   Fun1(x,y);//defined elsewhere (May be a normal method,class obj etc)
   Fun2(x,y);//Defined elsewhere
   MyClass.StatClassFun(x,y);

   //.
   //.
   //Etc and so on
   }

Which i guess can be done by the delegate. So what is the difference.
Does using delegates give better execution speed with less memory consumption? ??

[edit]Code block added - OriginalGriff[/edit]

Posted 27-Jun-11 21:03pm

asjadazeez

Updated 27-Jun-11 21:09pm

OriginalGriff

v2

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5 solutions

Solution 1

You should just have googled[^] it.

Seeing your sample I would suggest you to learn from http://msdn.microsoft.com/en-us/library/ms173171(v=vs.80).aspx[^]

Posted 27-Jun-11 21:09pm

Prerak Patel

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Sergey Alexandrovich Kryukov 28-Jun-11 3:12am

Makes sense, my 5.
I can offer my original works; please see my answer; many say they are interesting.
--SA

Solution 4

Delegates 101 - Part I: What is a Delegate?[^]

This is the best solution ever i seen.

Posted 27-Jun-11 21:16pm

CS1401

Solution 5

Delegates are different from normal methods in that they allow you to call them without knowing which method you are calling at compile time. They don't do anything that can't be done with normal method calls, but they do allow code to be simpler and cleaner:

enum function
   {
   callPrintScreen,
   callPrintPrinter,
   callPrintPDF
   }
private function func;
...
   func = function.callPrintPDF;
...
   switch (func)
      {
      case function.callPrintScreen:
         PrintScreen(myString);
         break;
      case function.callPrintPrinter:
         PrintPrinter(myString);
         break;
      case function.callPrintPDF:
         PrintPDF(myString);
         break;
   }

Becomes:

        private delegate void DoFunc(string s);
        private DoFunc func; 
...
            func = PrintPDF;
...
            func(myString);

If you need to add a new option (say PrintConsole), then you don't have to change the code which uses it at all - just the code that loads the delegate.

Posted 27-Jun-11 21:22pm

OriginalGriff

Solution 3

You can pick up a good book on C# and go through the chapter on delegates. That should help you get started.

Posted 27-Jun-11 21:13pm

Abhinav S

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-06-27T21:10:00

For example, you may want to see my article: Dynamic Method Dispatcher[^]. In particular, see section 6 which shows something not resolved elegantly enough with other methods.

Another short article Tips/Trick article is Simple Blocking Queue for Thread Communication and Inter-thread Invocation[^], see the code sample where queue type is a delegate type.

All this has nothing to do with performance of memory consumption (which are quite good). Delegate is additional abstraction tool adding a lot of flexibility compared to older versions of OOP before introduction of delegates.

Please see also the following interesting discussions (with my answers, with some examples):
Pass a method with N params as parameter in C#[^],
What are the advantages of delegates in C#.NET?[^],
Confusion about delegates[^].

—SA