Visual Basic

29-Aug-07 21:20

I am making a custom control which inherits from panel. This Control contains a collection field which will build a collection of another control (which also inherits from panel) in the form of List(of T). So far i have created my items (the second panel object) and during design time can go into the collection editor and add multiple items, yet when i close the collection ediotor and reopen it, the items in the collection have disappeared or are not visible in the collection builder anymore.

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Tom Deketelaere29-Aug-07 21:35

29-Aug-07 21:35

if the collection editor is you're first custom control wich contains the list(of T) then this behavior is normal. since you have closed the control containing the collection the collection has been destroyed when you reopen it a new collection (empty) is created.
If you want to keep the items in the collection even after closing it you have 2 options:

1) you save it to a db or file
2) you put the collection (list(of T)) not in you collection editor but in the form that contains the collection editor and when you open the collection editor you then give the list to it (you can do this with a public shared property and a few other methods)

hope this helps

The ANZAC29-Aug-07 21:42

29-Aug-07 21:42

ok...i sought-of follow you, maybe i should rephrase what i'm actually trying to do. I'm basically trying to add lots of panels to one panel through a collection property. This collection property is: PanelItem is the second control and this property exists on the first control.

Dim p_Collection as List(Of PanelItem)<br />
<br />
Public Property Collection() As List(Of PanelItem)<br />
    Get<br />
        Return p_collection<br />
    End Get<br />
    Set(ByVal value As List(Of PanelItem))<br />
        p_collection = value<br />
    End Set<br />
End Property

Now, when, in design mode, i click the ... button in the collection property of the first control it opens a collection editor, to this i can add, panelitems. Once i have done this and i close it. I then reopen this editor and find that no objects are now in it, yet when i go to add a new one, the number appended to the end automatically begins at 1 past the last one i added previously.

So my questions are:
Why is this happening?
What methods,subs etc do i use without using a database?
How do i get it to function like the treeview Node Collection Editor or similar?

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Tom Deketelaere29-Aug-07 21:54

29-Aug-07 21:54

my first guess would be that you forgot to display the items already in the list. That would result in not being able to see the items but that they are there.
In the load of you're second control (the collection editor) you should put something like this:
if p_collection.count >0 then
for each p as panelitem in p_collection
'display it
next
end if

without more code I can't really be shure about it

if you want to store this collection even after you're application has shutdown you will have to use a database or file or you can look into serialisation (not shure if its spelled correctly D'Oh! | :doh:

)

I'm not familiar with the treeview node collection editor but I'll take a look at it on my break Poke tongue | ;-P

The ANZAC29-Aug-07 21:57

29-Aug-07 21:57

no i'm not trying to store a collection after i've shutdown the application, i'm trying to achieve functionality similar to a treeview. Go into a new project and add a treeview to the form, then add to it's nodes property a few nodes, then close the collection editor of the treeview and reopen it, the nodes you added are available to be edited, this is what i'm trying to achieve.

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Tom Deketelaere29-Aug-07 22:22

29-Aug-07 22:22

Ok I took a look at it Poke tongue | ;-P

(first time I did it that way Poke tongue | ;-P

I always do it in code)

I would think that the way you do it should work. Can you provide me with the load of the collection editor or/and constructor. that way I can try to reproduce the error you have and search for a solution

The ANZAC29-Aug-07 22:25

29-Aug-07 22:25

well what i've already shown you is all i've done, it's not real complex, just two controls that inherit Panel and one has the property i've already shown, in this way it creates its own collecton editor without me having to do it manually, but i'm starting to think that i should be doing it manually, how would i go about that?

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Tom Deketelaere29-Aug-07 22:40

29-Aug-07 22:40

Ok I'v recreated you're problem I'll take a look at it on my break wich is in about 2hours and let you know

The ANZAC29-Aug-07 22:40

29-Aug-07 22:40

Thanks a heap.

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Tom Deketelaere29-Aug-07 22:54

Re: Custom Control Collection [modified]

29-Aug-07 22:54

Just stumbled on to something. I can't keep myself from trying to solve this (don't know why Poke tongue | ;-P

)

Here is the problem: a panel hasn't got a collection property by default so the collection editor (wich only displays because the property is a list) doesn't know what to do with it.

At first glance I don't think you will be able to achieve that what you want with a panel. Perhaps inheriting from a treeview will work better or a listview. But whitout knowing what exactly this custom control has to accomplish I don't know wich will be better.

Another option is ofcourse to do everything manually but I can't help you with that (haven't done that) and it is probably going to be alot of work. You'll probably have to draw the control you'r self.

If you tell me what functionality you are trying to accomplish perhaps I can help you search for a way to do that

Tom Deketelaere29-Aug-07 23:12

29-Aug-07 23:12

I just can't stop searching D'Oh! | :doh:

but I found a possibilaty
to accomplish something like this you have to use a property that already exists in a standerd panel and the only one that exists is the controls property so in you first custom control change you're property to this:

Private p As List(Of mainsub)
Public Overloads Property controls() As List(Of mainsub)
    Get
        Return p
    End Get
    Set(ByVal value As List(Of mainsub))
        p = value
    End Set
End Property

you can change the name of p and of mainsub but not of the property. the property must be controls
if you do this the collection editor will work

hope this helps

-- modified at 5:24 Thursday 30th August, 2007

there still seems to be a problem when you run the prog I take another look at it on my break (really need to get back to work now;P)

The ANZAC29-Aug-07 23:58

29-Aug-07 23:58

WOW! You've been a great help, haven't had a chance to try this stuff yet and the one below looks helpful also, i agree, it's an annoying puzzle that you hope has a simple answer and wel...it might not but thankyou heaps.

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