VB Forum / General 2 / March 2004

arnie <hrvoje.kol.@hi.htnet.hr> schreef in berichtnieuws
c2f0r0$a6k$1@ls219.htnet.hr...

Hello arnie,

1) don't shout, *please* :-\ :-)

2) You don't.   What you *can* do is to tell the ListBox to insert your
string at a specific (choosen by you) place into the existing list.   Look
into your Help-file under "AddItem" to see how.

Regards,
 Rudy Wieser

two methods come quickly to mind:

-load to an array
-sort the array randomly
-add array to lit

or,

-load to listbox, randomly setting the AddItem's Index property

A sort for the first solution can be found at
http://vbnet.mvps.org/code/sort/qsvariations.htm. The second solution just
takes your random number as the index, but (there's always a but)  there are
at least two problems with this second method:

1) you can't use the Index to assign a value to an empty list (the index is
used to replace data, not normally add it)

2) is you may get the same number twice, and adding an item to a list to an
index already populated will replace the current entry.  Thus you need some
way of determining if a particular index has a

You can get around (1) by adding blank data to the list. This is
unconventional, but it works ...

Dim x As Long
For x = 1 To 20
  List1.AddItem ""
Next

List1.AddItem "hello world", 4

(where 4 would be replaced with your random number)

The second requires you to track the indices used. To do this there are at
least 4 solutions that come to mind:

1 (ugly): test to see if an item exists at a particular index, and handle
the error if it doesn't

private function DoesItemExist(lst as listbox, index as long) as Boolean
  dim x as string
  on error goto listadd_error
  DoesItemExist = lst.list(index) > -1

listadd_exit
  exit function
listadd_error
  DoesItemExist = -1
  resume listadd_exit

end function

2 (just as ugly) : create a parallel array containing just numbers
representing the indices to use in adding the items, and maintain a flag
tracking which has been used ...

 dim flags(0 to totaltoadd) as Boolean

 <code to generate random number>
  if flags(randomnumber)= false then
      flags(randomnumber) = true
      list1.additem thedata, randomnumber
 else
      'handle case where item is used
  end if

3 (pretty ugly still): similar to 2, create a parallel array containing just
numbers representing the indices to use, pre-sort that array randomly and
use each sequential item as the add index ...

 dim arrayofnumbers(0 to 9) '10 items
 for x = 0 to 9
     arrayofnumbers(x) = x
  next x

   <random sort arrayofnumbers>

  for x = 0 to 9
      list1.additem "the data", arrayofnumbers(x)
   next

4 (no better than the others): use a collection, trap errors when adding to
an existing item

Personally, I find the very first suggestion the easiest to implement (add
to array, sort array, add to list).

Arnie,

Here's a link to a previous post where I provided code for "shuffling" an
array (watch for word-wrapping)...
http://groups.google.com/groups?selm=bh9746%24vm50a%241%40ID-201199.news.uni
-berlin.de&oe=UTF-8&output=gplain

If you don't need to visibly show the list to the user, using an array would
be a better approach.  But I assume you're using a listbox because you need
the list shown or require selectability... it'll be easy to adapt the code
at the link to shuffle a listbox instead.

HTH