>Trying to cast an object to it's interface well, that would be like trying
to turn a person into a painting.
Dave, your anology is wrong. It's perfectly valid to cast an object to an
interface it supports. Inclusive you don't even need to explicitly cast it:

IMammal m3 = m2;

Only when going the other way around you need to cast:
Managers.Add((Manager)m3);


Santiago, the problem you're having is that Generics in C# are "invariants".
A List<Person> is completely unrelated with List<Manager>, although Manager
inherits from Person.

Maybe this blog post will help you:
http://blogs.msdn.com/rmbyers/archive/2005/02/16/375079.aspx

If all you care is to have a list with the same elements, than you can just
create a new list and copy the original list in.

List<Person> persons = new List<Person>(Managers.ToArray());


Best Regards,
Paulo Carreiro


-----Original Message-----
From: StrongTypes@yahoogroups.com [mailto:StrongTypes@yahoogroups.com] On
Behalf Of santiago.perez@...
Sent: 05 June 2006 20:10
To: StrongTypes@yahoogroups.com
Subject: Re: [StrongTypes] Casting a SortedList Generic Class to a generic
Class of base type.

Hey Dave thanks for your help and insight into casting to an Interface. I
understand what you mean, and I follow your example to the T. My only
problem is that I want Cast a list of one type to it's base which youdidn't
have an example of, something like this:

List<Person> Persons =Managers ;

DO I need to specifically cast it as follows?:
List<Person> Persons =(List<Person>)Managers ;

NO matter what I try I can't cast a list of a sublass to it's base. This
doesn't seem like something that MS wouldn't have thought about.


Thanks again.

Santiago Perez
Florida's Turnpike Enterprise
Programmer Analyst

Pompano Operations
Ph 954-975-4855 ex 1127
Cell 954-444-9429



"Dave Cline"
<davecline@gmail.
com> To
Sent by: StrongTypes@yahoogroups.com
StrongTypes@yahoo cc
groups.com
Subject
Re: [StrongTypes] Casting a
06/04/2006 06:08 SortedList Generic Class to a
PM generic Class of base type.


Please respond to
StrongTypes@yahoo
groups.com






I'm not expert, in anybody's book, but I believe you're trying to use an
interface like a base class. An interface is really just a signature, a
template if you will. It does not represent inheritance. Trying to cast an
object to it's interface well, that would be like trying to turn a person
into a painting. It can't be done without breaking a few laws of nature not
to mention Newtonian physics. But you can turn a person into a child, or
senior citizen or mammal or vertebrate. A picture of a person is really just
a plan, a image of a three dimensional entity.

Try not using an interface as a generics type. Below was my testing rig.

But I maybe way off here.

DC


//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
using System;
using System.Collections.Generic;
using System.Text;

namespace InterfaceTesting
{
class Program
{
static void Main(string[] args)
{
System.Console.WriteLine("Testing Inheritance");

Manager m1 = new Manager();
m1.Name = "Manager M1";
System.Console.WriteLine("1:" + m1.Name);

Person p1 = (Person)m1;
System.Console.WriteLine("2:" + p1.Name);

List<Manager> Managers = new List<Manager>();

List<Person> Persons = new List<Person>();

List<Pet> Pets = new List<Pet>();

Manager m2 = new Manager();
m2.Name = "Manager M2";

Managers.Add(m2);

Persons.Add(m2);

//Pets.Add(m2); // although Pet implements IMammal you can't
turn a manager into a pet - as much as we'd like to sometimes.

System.Threading.Thread.CurrentThread.Suspend();
}
}

interface IMammal
{
}

class Pet : IMammal
{
public string Name = String.Empty;
}

class Person : IMammal
{
public string Name = String.Empty;
}

class Manager : Person
{
public string Title = String.Empty;
}
}










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