Traversing a Collection

1 May 2006 6:15 AM

James

Hi.

I have created several Collection objects which inherit from

System.Collections.CollectionBase

but up until now I've been able to process them according to the order
I populate them from a database.

Now I want to be able to traverse backwards and forward through items
in my collection and apart from loading the whole collection into an
array or Arraylist, I can't work out how.

eg. I have items like "Book" and a collection like "Books".

I can easily process the items with
For each book as Book in m_Books
' do stuff
Next

But I need more flexibility and the collection must have some kind of
index inherited from the CollectionBase

Maybe the arraylist idea is the best but I'm hoping that someone can
tell me about something more elegant that I must have at my fingertips
?

James.

1 May 2006 7:05 AM

Cor Ligthert [MVP]

James,

In Net is a complete main namespace for Database handling, that is
System.Data. (ADONET) In that are a lot of classes for the handling in
memory. A major part of those are than again collection classes.

There is probably a lot of time taken in that, it is a major part. Why would
you do it on your own and ask us to help you with that?

Cor

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"James" <yajames2***@yahoo.com.au> schreef in bericht
news:1146464152.352714.120900@j73g2000cwa.googlegroups.com...
> Hi.
>
> I have created several Collection objects which inherit from
>
> System.Collections.CollectionBase
>
> but up until now I've been able to process them according to the order
> I populate them from a database.
>
> Now I want to be able to traverse backwards and forward through items
> in my collection and apart from loading the whole collection into an
> array or Arraylist, I can't work out how.
>
> eg. I have items like "Book" and a collection like "Books".
>
> I can easily process the items with
> For each book as Book in m_Books
> ' do stuff
> Next
>
> But I need more flexibility and the collection must have some kind of
> index inherited from the CollectionBase
>
> Maybe the arraylist idea is the best but I'm hoping that someone can
> tell me about something more elegant that I must have at my fingertips
> ?
>
> James.
>

1 May 2006 11:48 AM

Kerry Moorman

James,

Your custom collection class should implement a strongly-typed Item property
that returns an item from the collection using an index.

Here is an example:

    Default Public Property Item(ByVal Index As Integer) As clsStudent
        Get
            Return CType(Me.List.Item(Index), clsStudent)
        End Get
        Set(ByVal Value As clsStudent)
            Me.List.Item(Index) = Value
        End Set
    End Property

Kerry Moorman

Show quoteHide quote

"James" wrote:

> Hi.
>
> I have created several Collection objects which inherit from
>
> System.Collections.CollectionBase
>
> but up until now I've been able to process them according to the order
> I populate them from a database.
>
> Now I want to be able to traverse backwards and forward through items
> in my collection and apart from loading the whole collection into an
> array or Arraylist, I can't work out how.
>
> eg. I have items like "Book" and a collection like "Books".
>
> I can easily process the items with
> For each book as Book in m_Books
> ' do stuff
> Next
>
> But I need more flexibility and the collection must have some kind of
> index inherited from the CollectionBase
>
> Maybe the arraylist idea is the best but I'm hoping that someone can
> tell me about something more elegant that I must have at my fingertips
> ?
>
> James.
>
>

1 May 2006 11:57 PM

James

Yes!!. Thanks Kerry, that worked well (and very simple which is good).

I think that property will have to be a standard entry in every
collection class I can lay my hands on :-)

Thanks again.