What is the disadvantage if I don't implement IEnumerable<T>

[Tony Johansson]

Hello!

Below I have a working program.
I have one generic class called Farm<T>
with this header definition public class Farm<T: IEnumerable<Twh ere T :
Animal

Now to my question I changed the inheritance of the IEnumerable from the
generic IEnumerable<T>
to the generel IEnumerable and the program function just the same so no
difference occured.

So what advantage do I get if I implement the generic interface
IEnumerable<Tin stead of the
generell IEnumerable ?
Can you also give me some example that show on advantage to implement the
generic interface IEnumerable<T>?

I know that this IEnumerable<Tin herit from IEnumerable.

So as a summary I can't see what purpose or advantage I get when I
implement IEnumerable<Tin stead of
IEnumerable.?

using System;
using System.Collecti ons.Generic;
using System.Collecti ons;
using System.Text;

namespace ConsoleApplicat ion9
{
class Program
{
static void Main(string[] args)
{
Farm<Animalfarm = new Farm<Animal>();
farm.Animal.Add (new Cow("Jack"));
farm.Animal.Add (new Chicken("Vera") );
farm.Animal.Add (new Chicken("Sally" ));
farm.Animal.Add (new SuperCow("Kevin "));

farm.MakeNoises ();
Farm<CowdairyFa rm = farm.GetCows();
dairyFarm.FeedT heAnimals();

foreach (Cow cow in dairyFarm)
{
if (cow is SuperCow)
((SuperCow)cow) .Fly();
}
Console.ReadKey ();

}
}




public abstract class Animal
{
string name;
public Animal(string name)
{
this.name = name;
}

public string Name
{
get { return name; }
}

public abstract void MakeANoise();
public abstract void Feed();
}

public class Chicken : Animal
{
public Chicken(string name) : base(name) {}

public override void MakeANoise()
{
Console.WriteLi ne("{0} says 'cluck!'", Name);
}

public override void Feed()
{
Console.WriteLi ne(Name + " has been feed(Chicken)") ;
}
}

public class Cow : Animal
{
public Cow(string name) : base(name) {}

public override void MakeANoise()
{
Console.WriteLi ne("{0} says 'moo!'", Name);
}

public override void Feed()
{
Console.WriteLi ne(Name + " has been fed(Cow)");
}
}

public class SuperCow : Cow
{
public SuperCow(string name) : base(name)
{ }

public void Fly()
{
Console.WriteLi ne("{0} is flying!", Name);
}

public override void MakeANoise()
{
Console.WriteLi ne("{0} says 'here I come to save the day!'",
Name);
}

public override void Feed()
{
Console.WriteLi ne(Name + " has been feed(SuperCow)" );
}
}

public class Farm<T: IEnumerable<Twh ere T : Animal
{
private List<Tanimals = new List<T>();

public List<TAnimal
{
get { return animals; }
}

IEnumerator IEnumerable.Get Enumerator()
{
return animals.GetEnum erator();
}

public IEnumerator<TGe tEnumerator()
{
return animals.GetEnum erator();
}


public void MakeNoises()
{
foreach (T animal in animals)
animal.MakeANoi se();
}

public void FeedTheAnimals( )
{
foreach (T animal in animals)
animal.Feed();
}

public Farm<CowGetCows ()
{
Farm<CowcowFarm = new Farm<Cow>();
foreach (T animal in animals)
if (animal is Cow)
cowFarm.animals .Add(animal as Cow);
return cowFarm;
}
}
}

//Tony

[Jon Skeet [C# MVP]]

Re: What is the disadvantage if I don't implement IEnumerable&lt; T&gt;

Tony Johansson <johansson.ande rsson@telia.com wrote:

Below I have a working program.
I have one generic class called Farm<T>
with this header definition public class Farm<T: IEnumerable<Twh ere T :
Animal
>
Now to my question I changed the inheritance of the IEnumerable from the
generic IEnumerable<T>
to the generel IEnumerable and the program function just the same so no
difference occured.

In this particular program, yes.

So what advantage do I get if I implement the generic interface
IEnumerable<Tin stead of the
generell IEnumerable ?

You end up with a more strongly typed API. This enables things like
LINQ to Objects to work much more smoothly, and fewer casts which need
to be checked at execution time. (In fact your foreach loops ended up
needing execution time casts anyway, but that's often not the case.)

In general, when you *can* implement a generic interface instead of a
nongeneric one, it's a good idea to do so.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[Pavel Minaev]

Re: What is the disadvantage if I don't implement IEnumerable&lt; T&gt;

On Jun 19, 12:05 am, Jon Skeet [C# MVP] <sk...@pobox.co mwrote:

Tony Johansson <johansson.ande rs...@telia.com wrote:

Below I have a working program.
I have one generic class called Farm<T>
with this header definition public class Farm<T: IEnumerable<Twh ereT :
Animal

>

Now to my question I changed the inheritance of the IEnumerable from the
generic IEnumerable<T>
to the generel IEnumerable and the program function just the same so no
difference occured.

>
In this particular program, yes.
>

So what advantage do I get if I implement the generic interface
IEnumerable<Tin stead of the
generell IEnumerable ?

>
You end up with a more strongly typed API. This enables things like
LINQ to Objects to work much more smoothly, and fewer casts which need
to be checked at execution time. (In fact your foreach loops ended up
needing execution time casts anyway, but that's often not the case.)
>
In general, when you *can* implement a generic interface instead of a
nongeneric one, it's a good idea to do so.

In addition to all this, there is one more practical reason to
implement IEnumerable<T>: if you do that, then any method that takes
IEnumerable<Twi ll be able to work with your object (and also any
method that takes a plain IEnumerable, since, as you've noticed,
IEnumerable<Tex tends IEnumerable). For example, the vast majority of
LINQ methods require IEnumerable<T>. You can use
Enumerable.Cast <TResult>() method to create wrappers as needed, of
course, but, same as with plain casts, it gets tedious to write it
again and again, and there is an associated performance hit as well.