asked on

listbox1.selecteditem.tostring question

when using this code:

label3.text = listbox1.selecteditem.tostring

which i have found in a few examples on the web, doesnt seem to work, the listbox1 is bound to a dataset, everything seem to work great, but i get an error when the form loads and the label doesnt get updated, heres my full code:

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Try
Label3.Text = ListBox1.SelectedItem.ToString
Catch ex As Exception
MessageBox.Show(ex.ToString)
End Try
End Sub

the error is as follows:

system.nullrefernceexception:object refernce not set to an instance of an object.
at purchase_orders.jobsedit.listbox1_selectedindexchanged(object sender, eventargs e)

what i want to accomplish, is when a user clicks on an item in the listbox, the label displays the text from the listbox

dysasha

ASKER

with the try method, after the errors (one for each item in the listbox) the label3 displays:

system.data.datarowview

instead of needed text

CarlosMu

Can you show the code with wich you binded the listbox to the dataset. Did you set the Displaymember and Value member properties of the listbox

iboutchkine

Check if you fill the listbox in page_load event. It might reinitialize the listbox on and it does not have reference set.

dysasha

ASKER

heres the code thats sets the selectcommand and fills the dataset for the listbox (the listbox is bound to dsjoblist21)

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
Dim selitem As String
selitem = ComboBox1.Text
SqlDataAdapter2.SelectCommand.CommandText = "SELECT JobNumber FROM JobNumbers WHERE (Project = N'" + selitem + "') ORDER BY JobNumber"
DsJoblist21.Clear()
SqlConnection1.Close()
SqlConnection1.Open()
SqlDataAdapter2.Fill(DsJoblist21)
SqlConnection1.Close()
End Sub

i did set the datasource and datamember, but i did it in the listbox properties instead of via code

dysasha

ASKER

also, i treid adding this to the on load:

ListBox1.DisplayMember = "Text"

farzinm

Check whether any of the items in the listbox is selected before you assign the value of the selected item to the listbox
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Try
if (Listbox1.selectedindex <> -1) then
Label3.Text = ListBox1.SelectedItem.ToString
End If
Catch ex As Exception
MessageBox.Show(ex.ToString)
End Try
End Sub

dysasha

ASKER

we, i'm not sure if its a step forward.. but it looks better, the pop up error disappeared, even if i remove the try/catch statement, but the label still says:

system.data.datarowview

reguardless of which item i select..

any more thoughts?

farzinm

I dont know whether this is the solution to your problem or not but this is what I tried on a test page.
The OnSelectedIndexChanged event of the listbox did not fire for me until I changed the autopostback property to "true".
Dont know whether it will work in your existing code but you can give it a shot.
Good Luck!

dysasha

ASKER

The OnSelectedIndexChanged event of the listbox did not fire for me until I changed the autopostback property to "true".

huh? i cant locate this property

farzinm

Its a behaviour of the listbox. You will find it in the properties dialog (window) of the listbox.

dysasha

ASKER

sir, i've looked and looked, and i cant find it, are you by chance using vb.net? perhaps you could narrow it down a bit, what group are you seeing it in? and what else is near it, ive expanded all the groups, and i dont see it anywhere

farzinm

lol :) Alright you can try this on the page_load
sub page_load(sender As Object, e As EventArgs)
listbox1.autopostback=true
end sub

I am using webmatrix but I believe that VS.Net also has it in its properties window cant be sure though.

dysasha

ASKER

autopostback is not a memeber of system.windows.forms.listbox?

dysasha

ASKER

perhaps you are referencing something i am not?

Imports System.Windows.Forms
Imports System.Data are the imports ive used...

farzinm

You are right! We are not referencing to the same thing. I get a
Namespace or type 'Forms' for the Imports 'System.Windows.Forms' cannot be found.
Let me get back to u if I find something.

farzinm

I am referencing to System.Web.UI.WebControls.ListBox which I believe is always the default one with my webmatrix pages.

dysasha

ASKER

i see :( i was hoping i had found a solution

any other thoughts?

CarlosMu

If you are writting a Web page you should not be using
Imports System.Windows.forms

those are the imports for a Visual basic to run on a windows enviroment.

try to include the imports that farzinm is using instead.

dysasha

ASKER

hmm, scroll up a bit, i'm not writing a webpage

farzinm

just a thought ...maybe you need to add event handlers?

farzinm

ok ignore my previous comment I dont think you need to add handlers

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dysasha

ASKER

Dim theListBox As ListBox = DirectCast(sender, ListBox)
Label3.Text = theListBox.GetItemText(theListBox.SelectedItem)

was exactly what i was looking for, i wasnt aware of directcast... reccomend any good books that dont prattle on about hello world and filling a dataset? something more advanced, that doesnt assume you know vb6?

dysasha

ASKER

thanks again!