Need explanation on creating a custom collection.

[Ken Varn]

I want to create a custom collection class that is similar to something like
the System.Windows.Forms.Control.ControlCollection.

I notice that this collection implements IList, ICollection, IEnumrable, and
ICloneable. I have tried to create a similar class, but one thing that I
cannot seem to understand is that the ControlCollection provides overrides
to the interfaces with specific object types rather than the generic object
class. i.e., Add method accepts a Control type and not a generic Object
type as is specified in IList.

When I have tried to do the same, I cannot get the compiler to allow me to
specify a method with a more specific type as an override for the interface.
Can someone explain how to do this?

C# snippet example:

public class MyClass : IList
{
public virtual void Add(Control.Label MyLabel); // How can I implement
IList.Add with a specific type?

}

--
-----------------------------------
Ken Varn
Senior Software Engineer
Diebold Inc.
va***@diebold.com
-----------------------------------

[Ignacio Machin]

Hi Ken,

You can do so inheriting from CollectionBase. CollectionBase is intended to
be used for this, it use an ArrayList internally to keep the items and you
provide the methods (Add,Delete, etc ) with the signature that you need.

Here is an example from one of my projects:
As you can see the class use the InnerList to keep the items, and as the
only way to access it is using your class's interface you can assure that
all the elements are of your selected type.
public class LocationPointCollection:CollectionBase

{

public LocationPoint Insert( int index, LocationPoint newelem )

{

this.InnerList.Insert( index, newelem);

return newelem;

}

public LocationPoint Add( LocationPoint newelem)

{

this.InnerList.Add( newelem);

return newelem;

}
Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Ken Varn" <va***@diebold.com> wrote in message
news:uw**************@TK2MSFTNGP12.phx.gbl...

I want to create a custom collection class that is similar to something like the System.Windows.Forms.Control.ControlCollection.

I notice that this collection implements IList, ICollection, IEnumrable, and ICloneable. I have tried to create a similar class, but one thing that I
cannot seem to understand is that the ControlCollection provides overrides
to the interfaces with specific object types rather than the generic object class. i.e., Add method accepts a Control type and not a generic Object
type as is specified in IList.

When I have tried to do the same, I cannot get the compiler to allow me to
specify a method with a more specific type as an override for the interface. Can someone explain how to do this?

C# snippet example:

public class MyClass : IList
{
public virtual void Add(Control.Label MyLabel); // How can I implement IList.Add with a specific type?

}

--
-----------------------------------
Ken Varn
Senior Software Engineer
Diebold Inc.
va***@diebold.com
-----------------------------------

[Ken Varn]

Thanks! That clears things up a bit. I'll give that a try.

--
-----------------------------------
Ken Varn
Senior Software Engineer
Diebold Inc.
va***@diebold.com
-----------------------------------
"Ignacio Machin" <ignacio.machin AT dot.state.fl.us> wrote in message
news:Ow**************@tk2msftngp13.phx.gbl...

Hi Ken,

You can do so inheriting from CollectionBase. CollectionBase is intended to be used for this, it use an ArrayList internally to keep the items and you
provide the methods (Add,Delete, etc ) with the signature that you need.

Here is an example from one of my projects:
As you can see the class use the InnerList to keep the items, and as the
only way to access it is using your class's interface you can assure that
all the elements are of your selected type.
public class LocationPointCollection:CollectionBase

{

public LocationPoint Insert( int index, LocationPoint newelem )

{

this.InnerList.Insert( index, newelem);

return newelem;

}

public LocationPoint Add( LocationPoint newelem)

{

this.InnerList.Add( newelem);

return newelem;

}
Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Ken Varn" <va***@diebold.com> wrote in message
news:uw**************@TK2MSFTNGP12.phx.gbl...

I want to create a custom collection class that is similar to something

like

the System.Windows.Forms.Control.ControlCollection.

I notice that this collection implements IList, ICollection, IEnumrable,

and

ICloneable. I have tried to create a similar class, but one thing that I cannot seem to understand is that the ControlCollection provides overrides to the interfaces with specific object types rather than the generic

object

class. i.e., Add method accepts a Control type and not a generic Object
type as is specified in IList.

When I have tried to do the same, I cannot get the compiler to allow me to specify a method with a more specific type as an override for the

interface.

Can someone explain how to do this?

C# snippet example:

public class MyClass : IList
{
public virtual void Add(Control.Label MyLabel); // How can I

implement

IList.Add with a specific type?

}

--
-----------------------------------
Ken Varn
Senior Software Engineer
Diebold Inc.
va***@diebold.com
-----------------------------------