asp.net ListBox problem

[CattleRustler]

Hi everyone. I am using a webform listbox control on an aspx page. The list is populated with the file names from a particular directory. The weirdness starts in trying get the text of a selected item, I either get an error, a blank string, or a -1 of the SelectedIndex property, no matter which item is selected. This is very strange and doesn't happen in a winforms app, the list acts as expected. Are there any weird settings I am missing when using a webforms listbox?

 

Thanks in advance

James

[Derek Stone]

The SelectedIndex property returns the index of the item, not the item text.

[CattleRustler]

no, I know that, I said I was getting errors so I used the SelectedIndex to see what it's value was and no matter what is selected the index returns -1 !

[kahlua001]

Is ViewState enabled and do you check for IsPostBack?

[CattleRustler]

EnableViewState is True

IsPostBack ? I am not to keen on this (newbie to asp.net)

AutoPostBack is false

 

??

[CattleRustler]

The problem goes away if I manually populate the list with items from the Items Property Collection builder in the property sheet.

 

maybe how I am populating the list in the first place is the problem? Here is the code...

 

Private Sub PopulateList(ByVal sPath As String)
       Dim dir As Directory
       Dim fileArr() As String
       fileArr = dir.GetFiles(sPath)

       Dim intLoop As Integer

       lstFiles.Items.Clear()
       For intLoop = 0 To fileArr.GetUpperBound(0)
           lstFiles.Items.Add(CStr(fileArr.GetValue(intLoop)))
       Next intLoop
   End Sub

[kahlua001]

can u post your page_load sub

[CattleRustler]

Page Load is empty but the following code is used to populate the listbox, when I use an intermediary collection to hold the file names, then pull them out into the list, the list then behaves as expected...

 

Private Sub PopulateList(ByVal sPath As String)
       Dim dir As Directory
       Dim fileArr() As String
       fileArr = dir.GetFiles(sPath)

       Dim intLoop As Integer
       Dim intEnd As Integer = fileArr.GetUpperBound(0)
       Dim colFileNames As New Collection


       lstFiles.Items.Clear()

       For intLoop = 0 To intEnd
           colFileNames.Add(CStr(fileArr.GetValue(intLoop)))
       Next intLoop

       Dim strLooper As String
       For Each strLooper In colFileNames
           lstFiles.Items.Add(strLooper)
       Next

       colFileNames = Nothing
   End Sub

 

strange ?

[kahlua001]

I think the problem has to do with how you are making the selection. If you are posting back to the page, you might be loosing the selectedItem on your postback.

[evaleah]

The postback issue mentioned above is almost surely your problem. I have this with datagrids quite often. I use a hidden html control to hold the value I want to keep and actually use that value when I execute code. I populate the html control with the OnSelectedItemChange event.

 

HTH

 

Eva