help with generics

[mopicus]

hello all, i have two base classes, one inherits from bindinglist<>
i need baseobject contains a generic reference to collection that contains it

class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>

class baseobjectcolle ction<T> : BindingList<T> where
T:baseobject<ba seobjectcollect ion<T>>

i'm getting compile error with this. i'm not sure if it's a syntax error or
what i'm trying it's impossible, without generics of course not problem

class baseobject
{
private baseobjectcolle ction m_colRef;
}

thank you

[Joanna Carter [TeamB]]

"mopicus" <mo*****@discus sions.microsoft .com> a écrit dans le message de
news: A5************* *************** **...icrosof t.com...

| hello all, i have two base classes, one inherits from bindinglist<>
| i need baseobject contains a generic reference to collection that contains
it
|
| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>
|
| class baseobjectcolle ction<T> : BindingList<T> where
| T:baseobject<ba seobjectcollect ion<T>>
|
| i'm getting compile error with this. i'm not sure if it's a syntax error
or
| what i'm trying it's impossible, without generics of course not problem
|
| class baseobject
| {
| private baseobjectcolle ction m_colRef;
| }

Your attempt looks way too complicated !!! :-)

| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>

You don't want a base object to be bound to a collection, you want it to
contain a collection

class BaseObject
{
private BindingList<Bas eObject> m_colRef;

...
}

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

[mopicus]

thankyou but does not solve my problem
public class BaseObject
{
public BaseObjectColle ction<BaseObjec t> CollectionRef;
}

public class BaseObjectColle ction<T> : BindingList<T>
{
}

public class EmployeeCollect ion : BaseObjectColle ction<Employee>
{
}
public class Employee : BaseObject
{

public Employee()
{
EmployeeCollect ion emp = this.Collection Ref as EmployeeCollect ion;
// compile ERROR : invalid cast
}

}
i think this example best illustrates what i want
thankyou anyways


"Joanna Carter [TeamB]" escribió:

"mopicus" <mo*****@discus sions.microsoft .com> a écrit dans le message de
news: A5************* *************** **...icrosof t.com...

| hello all, i have two base classes, one inherits from bindinglist<>
| i need baseobject contains a generic reference to collection that contains
it
|
| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>
|
| class baseobjectcolle ction<T> : BindingList<T> where
| T:baseobject<ba seobjectcollect ion<T>>
|
| i'm getting compile error with this. i'm not sure if it's a syntax error
or
| what i'm trying it's impossible, without generics of course not problem
|
| class baseobject
| {
| private baseobjectcolle ction m_colRef;
| }

Your attempt looks way too complicated !!! :-)

| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>

You don't want a base object to be bound to a collection, you want it to
contain a collection

class BaseObject
{
private BindingList<Bas eObject> m_colRef;

...
}

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

[Joanna Carter [TeamB]]

"mopicus" <mo*****@discus sions.microsoft .com> a écrit dans le message de
news: 3E************* *************** **...icrosof t.com...

| public class BaseObject
| {
| public BaseObjectColle ction<BaseObjec t> CollectionRef;
| }
|
| public class BaseObjectColle ction<T> : BindingList<T>
| {
| }
|
| public class EmployeeCollect ion : BaseObjectColle ction<Employee>
| {
| }
|
|
| public class Employee : BaseObject
| {
|
| public Employee()
| {
| EmployeeCollect ion emp = this.Collection Ref as EmployeeCollect ion;
| // compile ERROR : invalid cast
| }
|
| }
|
|
| i think this example best illustrates what i want
| thankyou anyways

Sorry, but you are still over-engineering here and you are going to get
bitten by the covariance problems when you try to convert a
BindingList<Bas eObject> to BindingList<Emp loyee>; this simply won't work.
See many previous posts on covariance.

You don't need to subclass these generic classes, simply use them as they
are.

public class BaseObject
{

}

public class Employee : BaseObject
{

}

public class Company : BaseObject
{
private BindingList<Emp loyee> employees = new BindingList<Emp loyee>();

...
}

And I don't see why you would want to include a list of Employees in the
Employee class; this would mean that every single employee would also have a
list of *all* employees inside them ???

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

[Marc Gravell]

If I understand what you are trying to do, then you can do this with nested
classes (below); however, I should warn you that it will all go a bit freak
when you subclass - i.e. you can't really subclass the inner-class; anything
that inherits from BaseItem<T> will be stuck with the same collection
class - you can't really alter it.

Either class can be the inner; in this context I guess the collection is
less likely to change, so could sit on the inside? Personally, I'm not sure
that generics /nesting is the right answer here... perhaps the BaseItem
could have a BaseCollection reference, and then (on a class-by-class basis)
privide a "new OwnerCollection " implementation that casts this to the
correct collection type?

Marc

using System;
using System.Collecti ons.ObjectModel ;
using System.Componen tModel;

public class BaseItem<T> {
public T TypedValue; // only public for demo
public BaseCollection OwnerCollection ; // only public for demo

public class BaseCollection : BindingList<Bas eItem<T>> {
readonly Collection<Base Item<T>> items = new
Collection<Base Item<T>>();
}
}
public class SomeClass : BaseItem<int> { }

static class Program {
static void Main() {
SomeClass.BaseC ollection collection = new
SomeClass.BaseC ollection();
SomeClass item = new SomeClass();
item.TypedValue = 500;
collection.Add( item);
item.OwnerColle ction = collection;
}
}

[mopicus]

thank you both of you

i need inheritance from both baseitem and baseitemcollect ion. so I think
best option is take away collection reference from baseitem object.

anyways, it's a reference to the collection, not the collection itself,
isn't it? so there's nothing bad with it about memory usage, i think

i do a lot of work inside an object, removing itself from it's owner
collection, counting items, accessing others ... but i think I can try
another approach without the collection reference.

anyways nested class solution is a good example

again, lot of thanks

[Ben Voigt]

"mopicus" <mo*****@discus sions.microsoft .com> wrote in message
news:3E******** *************** ***********@mic rosoft.com...

thankyou but does not solve my problem
public class BaseObject
{
public BaseObjectColle ction<BaseObjec t> CollectionRef;
}
public class BaseObjectColle ction<T> : BindingList<T>
{
}
perhaps try instead:

public class BaseObject<T> where T : BaseObject

public class BaseObjectColle ction<T> : BindingList<T> where T :
BaseObject<T>

public class Employee : BaseObject<Empl oyee>

You'll have to decide in advance how specific your collections are...

You can get away with Employee, Manager, Salesperson all in a
EmployeeCollect ion, but then you won't be able to have a ManagerCollecti on
containing only Manager objects...

Because if Manager.Collect ionRef had type ManagerCollecti on, then you could
write
foreach (Manager m in CollectionRef)
but if it was really an EmployeeCollect ion, then some of the employees
aren't really managers.

If Manager.Collect ionRef has type EmployeeCollect ions, then you can't ever
store a Manager in a ManagerCollecti on, because although
foreach (Employee e in CollectionRef)
would be ok on a ManagerCollecti on,
CollectionRef.A dd(new SalesPerson())
would fail.

public class EmployeeCollect ion : BaseObjectColle ction<Employee>
{
}
public class Employee : BaseObject
{

public Employee()
{
EmployeeCollect ion emp = this.Collection Ref as EmployeeCollect ion;
// compile ERROR : invalid cast
}

}
i think this example best illustrates what i want
thankyou anyways


"Joanna Carter [TeamB]" escribió:

"mopicus" <mo*****@discus sions.microsoft .com> a écrit dans le message de
news: A5************* *************** **...icrosof t.com...

| hello all, i have two base classes, one inherits from bindinglist<>
| i need baseobject contains a generic reference to collection that
contains
it
|
| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>
|
| class baseobjectcolle ction<T> : BindingList<T> where
| T:baseobject<ba seobjectcollect ion<T>>
|
| i'm getting compile error with this. i'm not sure if it's a syntax
error
or
| what i'm trying it's impossible, without generics of course not problem
|
| class baseobject
| {
| private baseobjectcolle ction m_colRef;
| }

Your attempt looks way too complicated !!! :-)

| class baseobject<T> : where T:baseobjectcol lection<baseobj ect<T>>

You don't want a base object to be bound to a collection, you want it to
contain a collection

class BaseObject
{
private BindingList<Bas eObject> m_colRef;

...
}

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer