Hi,

i experimented with postback and viewstate. With this code, there are 2
dropdownlists created, one visible and with AutoPostBack true, the other not
visible and no AutoPostBack, and one button . The first time, when i choose
value "b" of DD1, the second DD appears. That's normal.

Now, what i don't understand is when i further click on the button (causing
a postback), the second DD remains visible. Don't think i don't want it. I
just don't uderstand.

After clicking the button, I thought the code would start from the very
begin, so setting DD2 again on not visible. And because the first DD1 has
not changed its selectedvalue, the procedure dropd changing DD2 into visible
will not be executed. So DD2 should stay invisible. But it's not.

Can somebody explain what's wrong in my way of thinking?
Thanks
Dan

Imports System.Collections.Generic
Partial Class _Default
   Inherits System.Web.UI.Page
   Friend dds As New List(Of DropDownList)

   Protected Sub Page_PreInit(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.PreInit
       Dim dd1, dd2 As DropDownList
       Dim z1, z2 As ListItem
       Dim lit As LiteralControl
       If Not IsPostBack Then
           dd1 = New DropDownList
           dd1.ID = "dd1"
           dd1.AutoPostBack = True
           z1 = New ListItem("a", "a")
           dd1.Items.Add(z1)
           z1 = New ListItem("b", "b")
           dd1.Items.Add(z1)

           dd2 = New DropDownList
           dd2.ID = "dd2"
           dd2.Visible = "false"
           z2 = New ListItem("a", "a")
           dd2.Items.Add(z2)
           z2 = New ListItem("b", "b")
           dd2.Items.Add(z2)

           dds.Add(dd1)
           dds.Add(dd2)
           form1.Controls.Add(dd1)
           form1.Controls.Add(dd2)
           Session("dds") = dds
       Else
           dds = CType(Session("dds"), List(Of DropDownList))
           For Each d As DropDownList In dds
               form1.Controls.Add(d)
           Next
       End If

       Dim bt2 As New Button
       form1.Controls.Add(bt2)
       AddHandler bt2.Click, AddressOf submit_Click

       For Each d As DropDownList In dds
           AddHandler d.SelectedIndexChanged, AddressOf dropd
       Next
   End Sub

   Protected Sub dropd(ByVal sender As Object, ByVal e As System.EventArgs)
       Dim dd As DropDownList = CType(sender, DropDownList)
       Session("sv" & dd.ID) = dd.SelectedValue

       If dd.ID = "dd1" And dd.SelectedValue = "b" Then
           FindControl("dd2").Visible = True
       ElseIf dd.ID = "dd1" And Not dd.SelectedValue = "b" Then
           FindControl("dd2").Visible = False
       End If
   End Sub

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

   End Sub
End Class