populating listbox using jscript and not postback

[collie]

Hi,

I have 2 listboxes. The first gets populated from the db as soon as
the page loads. The second listbox get populated based on the user's
selection from the first listbox. However, currently the code is
such that with each selection there is a postback. We want to avoid it
using filter and javascript. I am not using ADO.NET but adodbc and no
datagrids or datasets (please don't tell me that i should as my boss
clearly doesn't want to get into it at this stage).

How can i do it?

Thanks


Currently the code with the postback is as follows:
page_load

if not page.ispostback then
Do While Not rs.EOF
li = New ListItem(rs("cat_name").Value,
rs("cat_id").Value)
List1.Items.Add(li)
rs.MoveNext()
Loop

End If

'List1.SelectedIndex = 0
rs.Close()
rs = Nothing

List1.SelectedValue = cat_id

'here there is some other code not relevant to the
listboxes

'select items for second listbox
Dim rsSub As New ADODB.Recordset
rsSub.Open("SELECT sub_name, sub_id FROM subs WHERE
cat_id=" & cat_id.ToString & " ORDER BY sub_name ASC", cn)
Dim l_item As ListItem
Do While Not rsSub.EOF
l_item = New ListItem(rsSub("sub_name").Value,
rsSub("sub_id").Value)
List2.Items.Add(l_item)
rsSub.MoveNext()
Loop

List2.SelectedValue = sub_id

rsSub.Close()
rsSub = Nothing


cn.Close()
End If
' End If


End If

End Sub

Protected Sub Select1Change(ByVal sender As System.Object, ByVal e
As System.EventArgs)

Dim cn As New ADODB.Connection
cn.Open(YBayTools.Constants.ConnectionString)


Dim rs As New ADODB.Recordset
Dim li As ListItem

rs.Open("Select * from subs where cat_ID =" &
List1.SelectedItem.Value.ToString, cn)
'rs.Open("Select * from subs where cat_ID ='" &
List1.SelectedItem.Text.ToString & "' &
List1.SelectedItem.value.ToString", cn)


Dim strCat As String

If List2.Items.Count > 0 Then
List2.Items.Clear()
End If

If rs.BOF And rs.EOF Then
Response.Write("no records found")
Else

Do While Not rs.EOF
li = New ListItem(rs("sub_name").Value,
rs("sub_id").Value)
List2.Items.Add(li)
rs.MoveNext()

Loop


End If

rs.Close()
rs = Nothing

cn.Close()

 

[Jerry]

Sounds like the 'AutoPostback' property for the listbox is
set to True - change it to False...

Jerry

 

[collie]

Hi,

If i change the autopastback to false then it doesn't get the data
from the db. I need to rewrite the code using jscript.

I need to populate 2 listboxes from a db. When the page loads then the
first listbox needs to be populated and based on selection from that
listbox the second listbox needs to be populated accordingly with the
matching items.
However, my boss doesn't want the page to do a postback once an item
from the first listbox is selected. also, he doesn't want to use
ado.net but classic ado.
He wants to use jscript. I am writing my code in vb.net

I wrote a code but only the first listbox gets populated and when i
select an item then that item appears in the second listbox eg. if i
selected cars from the 1st listbox then cars will appear in the 2nd
listbox instead of BMW, HONDA etc.

I know that my code might be totally wrong as i have no idea what to
do.

My db has 2 tables called CATS with CAT_NAME (Such as cars) and
CAT_ID. The 2nd table is called SUBS and contains SUB_ID, CAT_ID and
SUB_NAME (such as Honda, BMW).It is very important that my code with
read the CAT_ID and SUB_ID as i have to use them later on.


Can someone please help me?

Thanks


Here is my code:

Dim objconn As New ADODB.Connection()
Dim rsx As New ADODB.Recordset()
Dim sLastManufacturer
Dim manufacturer As New ListBox()
objConn = Server.CreateObject("adodb.connection")
objConn.OPEN("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" &
Server.MapPath("/duclassified.mdb"))
rsX = Server.CreateObject("ADODB.Recordset")
rsx.Open("SELECT CAT_NAME, CAT_ID FROM CATS", objConn)

If rsX.EOF Then
Response.Write("No category.<BR>")

Else
' write the CATEGORY listbox...

Response.Write("<SELECT NAME=""manufacturer"" SIZE=15" & _
" ONCHANGE=""manuselected(this);"" >")
' write the entry code for the javascript...
Dim sJavaScript = "function manuselected(elem){" &
Environment.NewLine & _
"for (var i = model." & _
"options.length; i >= 0; i--){" & Environment.NewLine & _
"model.options = null;" & _
Environment.NewLine
' loop through the recordset...
Do Until rsx.EOF
' is this a new manufacturer?
Dim cat_names = rsx("cat_name").Value

If (sLastManufacturer) <> "CAT_Names" Then
' if so, add an entry to the first listbox
sLastManufacturer = rsx("CAT_Name").Value
Response.Write("<OPTION VALUE=" & rsx("CAT_ID").Value & ">"
& sLastManufacturer & "</OPTION>")
' and add a new section to the javascript...
sJavaScript = sJavaScript & "}" &
Environment.NewLine & "if (elem.options[elem.selectedIndex].value==" &
_
rsx("CAT_ID").Value & "){" & Environment.NewLine
& ""
End If
' and add a new model line to the javascript...
sJavaScript = sJavaScript & _
"model.options[" & _
"model.options.length] = new Option('" & _
rsx("CAT_NAME").Value & "','" & rsx("CAT_ID").Value
& _
"');" & _
Environment.NewLine
rsx.MoveNext()
Loop
' finish the manufacturer listbox...
Response.Write("</SELECT>")

rsx.Close()
rsx = Nothing
objconn.Close()
objconn = Nothing

' create the SUBS listbox...

Dim rsSubs As New ADODB.Recordset()
objconn = Server.CreateObject("adodb.connection")
objconn.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" &
Server.MapPath("/duclassified.mdb"))
rsSubs = Server.CreateObject("ADODB.Recordset")
rsSubs.Open("SELECT SUB_NAME, SUB_ID from SUBS where cat_ID =" &
manufacturer.SelectedItem.Value.ToString, objconn)
Response.Write("<SELECT NAME=""model"" SIZE=15>")
Response.Write("<OPTION>[none currently selected]</OPTION>")
Response.Write("</SELECT>")
' put the last line on the javascript...
' and write it out...
sJavaScript = sJavaScript & Environment.NewLine & "}" &
Environment.NewLine & _
"}" & Environment.NewLine
Response.Write("<SCRIPT LANGUAGE=""JavaScript"">" &
Environment.NewLine)
Response.Write(sJavaScript & Environment.NewLine & "</SCRIPT>" &
Environment.NewLine)
End If
End Sub

 

[manisekarant]

Change the following line in your code
If (sLastManufacturer) <> "CAT_Names" Then
as
If (sLastManufacturer) <> CAT_Names Then