Error Using SelectedIndicesof Listbox with custom objects

A

Alex Stevens

I'd already posted this in microsoft.public.dotnet.framework.windowsforms
and microsoft.public.dotnet.framework.windowsforms.controls to no avail so
apologies for the cross-posting.

Hi,

I'm writing a usercontrol which displays the typical two listboxes and the
ability to move items from one to the other.

The listboxes are populated with my custom objects (SwapItem), which simply
have a ValueMember, DisplayMember a couple of other properties and the
tostring function to display the DisplayMember in the listbox.

The issue I'm getting is with the SelectedIndices array
I selected four items in the listbox and then I use:

For i As Int32 = 0 To lstAvailable.SelectedIndices.Count - 1
lstItem =
CType(lstAvailable.Items.Item(lstAvailable.SelectedIndices(i)),
SwapListBoxItem)
lstItem.Selected = True
intIndex = i
Next

Before execution gets to this, the lstAvailable.SelectedIndices.count
returns 4.
Happy Days.

However when I try to evaluate lstAvailable.SelectedIndices(0) or
lstAvailable.SelectedIndices(1) or lstAvailable.SelectedIndices(2) or
lstAvailable.SelectedIndices(4) i get the error "Index was outside the
bounds of the array".
This can't be true as the.count is 4.

I get exactly the same results using the SelectedItems array to.
Is this a symptom of using my own custom object in the listbox (I've posted
the custom object code below for reference)??

Once the custom object is instantiated and then populated I use this line to
add it to the listbox:
lstAvailable.Items.Add(SwapItem)

Also, when I use:
Dim lst As SwapListBoxItem
For Each lst In lstAvailable.SelectedItems
lstItem.Selected = True
Next

The lstAvailable.SelectedItems.Count returns 4, but the execution doesn't
iterate, just jumps over the For statement.
However, I can use this and it iterates correctly:

Dim lstItem As SwapListBoxItem
For Each lstItem In lstSelected.Items
lstItem.Selected = True
Next

So it seems that the items collection can iterate my customer objects but
the selecteditems cannot????

Thanks

Alex

*****Custom Object Code Start******
Public Class SwapListBoxItem

Private m_objValueMember As Object = ""
Private m_strDisplayMember As String = ""
Private m_bolSelected As Boolean = False

Public Property ValueMember() As Object
Get
Return m_objValueMember
End Get
Set(ByVal ValueMember As Object)
m_objValueMember = ValueMember
End Set
End Property

Public Property DisplayMember() As String
Get
Return m_strDisplayMember
End Get
Set(ByVal DisplayMember As String)
m_strDisplayMember = DisplayMember
End Set
End Property

Public Property Selected() As Boolean
Get
Return m_bolSelected
End Get
Set(ByVal Selected As Boolean)
m_bolSelected = Selected
End Set
End Property

Public Sub ChangeSelected()
m_bolSelected = Not m_bolSelected
End Sub

Public Overrides Function ToString() As String
Return Me.DisplayMember
End Function

End Class

*****Custom Object Code End******
 
O

One Handed Man \( OHM#\)

Remember, you are returning a collection of indicies so you should use the
follwing to access a particular element

ListBox1.SelectedIndicies.Item( numOfElement )

OHM
 
A

Alex Stevens

Well, that was irritating.......

I copied the code into a new project to attach to this message.
Added a new listbox to a new form and hooked up the code.

Guess what....it worked.

I then gradually worked back to the original form (which is actually a
custom control), and ended up simply deleting the listbox on the control,
and adding a new one and renaming it.

Guess what it started to work again.
(I wondered why there weren't many posting with the same syptoms).

Also, lstAvailable.SelectedIndices(i) works just the same as
lstAvailable.SelectedIndices.Item(i)

I wish I could invoice MS for what was a day or so of my time!!!
 
O

One Handed Man \( OHM#\)

Actually, I tested this and got the same error, it was only when I used
..Item that it worked consistantly, I found Once I had encountered the error
once, I ket getting it by omitting the .Item

One would think that Item would be the default property to enable you to use
parenthasis directly after the object, but I had to consistently use item
for good results.

Regards - OHM
 
H

Herfried K. Wagner [MVP]

* "Alex Stevens said:
I'm writing a usercontrol which displays the typical two listboxes and the
ability to move items from one to the other.

The listboxes are populated with my custom objects (SwapItem), which simply
have a ValueMember, DisplayMember a couple of other properties and the
tostring function to display the DisplayMember in the listbox.

The issue I'm getting is with the SelectedIndices array
I selected four items in the listbox and then I use:

For i As Int32 = 0 To lstAvailable.SelectedIndices.Count - 1
lstItem =
CType(lstAvailable.Items.Item(lstAvailable.SelectedIndices(i)),
SwapListBoxItem)
lstItem.Selected = True
intIndex = i
Next

Before execution gets to this, the lstAvailable.SelectedIndices.count
returns 4.
Happy Days.

However when I try to evaluate lstAvailable.SelectedIndices(0) or
lstAvailable.SelectedIndices(1) or lstAvailable.SelectedIndices(2) or
lstAvailable.SelectedIndices(4) i get the error "Index was outside the
Click to expand...

There is no 'SelectedIndices(4)' if count is 4. But the loop above
should only run up to index 3.
Also, when I use:
Dim lst As SwapListBoxItem
For Each lst In lstAvailable.SelectedItems
lstItem.Selected = True
Next
Click to expand...

The code won't compile because there is no 'lstItem' variable...
 
O

One Handed Man \( OHM#\)

Hi Herfried,

Thats not the issue, look at my last post on the subject.

Regards - OHM ( One Handed Man - Terry Burns )
 
O

One Handed Man \( OHM - Terry Burns \)

Trust me there is no error in the OP post. I duplicated this myself. See my
post, and try it yourself, you will be suprised.

--

OHM ( Terry Burns )
. . . One-Handed-Man . . .
 
H

Herfried K. Wagner [MVP]

* "One Handed Man \( OHM - Terry Burns \) said:
Trust me there is no error in the OP post. I duplicated this myself. See my
post, and try it yourself, you will be suprised.
Click to expand...

I suggest you have a look at the OP's code and what I have written...
 
O

One Handed Man \( OHM - Terry Burns \)

I have and you still have not tried it have you ?

--

OHM ( Terry Burns )
. . . One-Handed-Man . . .
 
C

Cor Ligthert

Hi Terry,

Forget it, we both know Herfried, young, brilliant, has still a lot to
learn, however we like him.

:)

Cor
 
H

Herfried K. Wagner [MVP]

* "One Handed Man \( OHM - Terry Burns \) said:
I have and you still have not tried it have you ?
Click to expand...

I never said that your suggestion is wrong...
 

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