Do delegates don't respect polymorphisms -- why?

say in this example:

using System;

public delegate string FirstDelegate (int x);


abstract class Base
{
public abstract string Foo(int );

public void Dispatch()
{
FirstDelegate del=new FirstDelegate (Foo);
del(5);
}
}



class Derived
{
public override string Foo(int x)
{
return " "+x;
}
}


class Runner
{

public static void Main()
{
Derived d=new Derived();
d.Dispatch(); //trys to delegate bases
}
}


The same thing happens when Base is NOT abstract class and Foo is
declared as virtual....

Is there a rule don't mix delegates and runtime polymorphism???

Hi,

why should delegates not respect polymorphisms ?
This code, works as expected for me. FirstDelegate
points to the implementation of Foo(..) in Derived.
The only thing that leads to a StackOverflowException is
doing

class DerivedOverflow : Derived
{
public override string Foo(int x)
{
return "-" + base.Dispatch();
}
}

which is also expected behaviour from my understandings.

Perhaps you could explain a little more what you mean.

Philipp



puzzlecracker schrieb:
> Do delegates don't respect polymorphisms -- why?
>
> say in this example:
>
> using System;
>
> public delegate string FirstDelegate (int x);
>
>
> abstract class Base
> {
> public abstract string Foo(int );
>
> public void Dispatch()
> {
> FirstDelegate del=new FirstDelegate (Foo);
> del(5);
> }
> }
>
>
>
> class Derived
> {
> public override string Foo(int x)
> {
> return " "+x;
> }
> }
>
>
> class Runner
> {
>
> public static void Main()
> {
> Derived d=new Derived();
> d.Dispatch(); //trys to delegate bases
> }
> }
>
>
> The same thing happens when Base is NOT abstract class and Foo is
> declared as virtual....
>
> Is there a rule don't mix delegates and runtime polymorphism???
>

What same thing? Unfortunately, you haven't pasted the exact code [it
doesn't compile...], so we can't know what you are seeing, since any
repairs we make may change the problem...

However, making the most obvious fixes (adding a base class, naming
the argument, etc) - it all works fine and the override in Derived is
called.

Delegates respect polymorphism.

Perhaps tell us what you are seeing?

Marc
[C# MVP]

On Oct 21, 10:06*am, Philipp Brune <her...@gmx.de> wrote:
> Hi,
>
> why should delegates not respect polymorphisms ?
> This code, works as expected for me. FirstDelegate
> points to the implementation of Foo(..) in Derived.
> The only thing that leads to a StackOverflowException is
> doing
>
> * class DerivedOverflow : Derived
> * * *{
> * * * * *public override string Foo(int x)
> * * * * *{
> * * * * * * *return "-" + base.Dispatch();
> * * * * *}
> * * *}
>
> which is also expected behaviour from my understandings.
>
> Perhaps you could explain a little more what you mean.
>
> Philipp
>
> puzzlecracker schrieb:
>
> > Do delegates don't respect polymorphisms -- why?
>
> > say in this example:
>
> > using System;
>
> > public delegate string FirstDelegate (int x);
>
> > abstract class Base
> > {
> > *public abstract string *Foo(int );
>
> > * * * public void Dispatch()
> > * * * {
> > * * * * * * FirstDelegate *del=new FirstDelegate (Foo);
> > * * * * * * del(5);
> > * * }
> > }
>
> > class Derived
> > {
> > * * *public override string *Foo(int x)
> > * * * {
> > * * * * * *return " "+x;
> > * * *}
> > }
>
> > class Runner
> > {
>
> > * * * * public static void Main()
> > * * * * {
> > * * * * * * * Derived d=new Derived();
> > * * * * * * * d.Dispatch(); //trys to delegate bases
> > * * * * }
> > }
>
> > The same thing happens when Base is NOT abstract class and Foo is
> > declared as virtual....
>
> > Is there a rule don't mix delegates and runtime polymorphism???

Great! let me get the debug, i thing my telling compiler to think
Base is Base.....