delegate question

[tzzdvd]

Hi to all,
I have a question about the delegate
Example

public void delegate myDel();
public class myClass
{
   ...
   public myDel d;
}

public class Container
{
   List<myClass> lst = new List<myClass>();
   void AddFiveValues()
   {
      for (int i = 0; i < 5; i++)
      {
         myClass m = new myClass();
         m.d = new myDel(FunctionUsed); // <<<===
         lst.Add(m);
      }
   }

   void FunctionUsed()
   {
      ...
   }
}

This I think is a correct association of the delegate function.
Somewhere I have seen that is possible to use this sintax

m.d = FunctionUsed;

without the "new" statement.
I have tried it and I didn't receive any error or any runtime problem (apparently)
The reason, I think, is that the FunctionUsed matches the delegate structure

What is the difference between these two approach?

Thanks'

Davide

 

[jmeckley]

the delegate is just a contract signature. how it's fulfilled doesn't matter, only that the signature is the same.

once the delegate is defined you can invoke it with the proper parameters. example

private delegate string IntergerToString(int i);
private IntergerToString the_implementation;

private string explicit_implementation(int x)
{
   return x.ToString();
}

public void Convert()
{
   the_implementation = explicit_implementation;
   Console.WriteLine(the_implementation(1))
}

or you can use anonymous delegates

public void Convert()
{
   the_implementation = delegate(int a_number) {return a_number.ToString();};
   Console.WriteLine(the_implementation(1))
}

with .net 3.0 lamba expressions allow the syntax to be even shorter.

the_implementation = x=>x.ToString();

Jason Meckley
Programmer
Specialty Bakers, Inc.

 

[tzzdvd]

Thanks Jason,
I know how the delegate functions.
My question is quite different.

I would like to understand the difference between

m.d = new myDel(FunctionUsed);

and

m.d = FunctionUsed;

assignment, in particular when the same function is assigned to multiple istance of a class.

Davide

 

[jmeckley]

oh. i would be interested in that too

Jason Meckley
Programmer
Specialty Bakers, Inc.

 

[phinoppix]

interesting indeed. any luck from ildasm? i'll try digging tomorrow too; i don't have .net on my machine now.