DropDownList.SelectedIndexChanged

I have 2 dropdown lists on one page. A selection from the first list
determines what gets listed in the second list.
but the problem nothing appears in list2.


the following code

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Put user code to initialize the page here
DropDownList1.Items.Add("a")
DropDownList1.Items.Add("b")
End Sub

Private Sub DropDownList1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
DropDownList2.Items.Clear()
Dim a As Integer
a = DropDownList1.SelectedIndex
If a = 0 Then
DropDownList2.Items.Add("selected a")
Else
DropDownList2.Items.Add("selected b")

End If
End Sub
plz help me
thanx
sara

Set the AutoPostBack property for DropDownList1 control to true.

If this property is set to false then the function DropDownList1_SelectedIndexChanged will not be called at all.

~Nikhil

Thank u very much

Dear Nikhil
the proble was solved but still i have another problem
with every selection for list2, the items are duplicated in list 1.

Im guessing you are populating List 1 on the PageLoad event. What is happening is that items are bieng re-added to List1 every time the Page makes a round trip to the server.

Place the List1 data population code in a If block where you check if the page has been posted back or not.

VB Code:

If Not IsPostBack Then
            'Code to add items to list 1
            DropDownList1.Items.Add("1")
            DropDownList1.Items.Add("2")
            DropDownList1.Items.Add("3")
End If

~Nikhil

Dear Nikhil
it is working good now
thank u very much for ur help