updatepanel - making other control on page visible or invisible - asp.net

Question

I'm using a update panel to display some results on a page and it is working fine with no probs.
If though no results were returned I would like a message to display - saying no records found.
The trouble is getting the asp:panel(pnlNoUsers) visible option to be true or false(which contains the no records found message is the prob I'm having
My code for for the update panel is:
<asp:UpdatePanel ID="pnlCust" runat="server">
<ContentTemplate>
<asp:Panel ID="pnlNoUsers" runat="server" visible="false">
<div class="inner-page-title">
<h2>
No records found.</h2>
</div>
</asp:Panel>
<%=show_cust()%>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnRefresh" />
</Triggers>
</asp:UpdatePanel>
The show_cust() function simply returns a string which will be displayed on the page:
If bHasUsers = False Then
pnlNoUsers.Visible = True
Return ""
End If
pnlNoUsers.Visible = False
Return strUsers & "</ul>"
The panel "pnlNoUsers"visibility property isn;t changing at all?
Anyone know how I can do this?
Thanks,

Answer 1

I don't know the complexity of your requirement but you can skip the conditional logic altogether by using a data control. You can use a gridview control which has an
EmptyDataText property that you can use.
MSDN: Gridview EmptyDataText property
You can manually bind the gridview control with data using DataSource & dataBind properties.

Answer 2

Without your button click event, it is difficult to determine where you might be going wrong. A couple ideas though: Set UpdateMode to Conditional, this is a normal mode to have update panels in, get rid of your inline response write, that is not a good way to handle ASP.NET data display, and add a Literal tag that you can render the user's list. As Damien mentioned, I would use a ListView, Repeater, or GridView (in that order) to render your user list rather than generating an unordered list in code and writing it to the browser.
<asp:UpdatePanel ID="pnlCust" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Panel ID="pnlNoUsers" runat="server" Visible="false">
<div class="inner-page-title">
<h2>No records found.</h2>
</div>
</asp:Panel>
<asp:Literal ID="CustomerListLiteral" runat="server" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnRefresh" />
</Triggers>
</asp:UpdatePanel>
<asp:Button ID="btnRefresh" runat="server" OnClick="btnRefresh_Click" />
Handle your update panel efforts in a button click event. My bet is that the response write you had inline was not triggering the update panel to work. This should do what you want.
Protected Sub btnRefresh_Click(sender As Object, e As EventArgs)
Dim bHasUsers As Boolean = False
Dim strUsers As String = String.Empty
If bHasUsers = False Then
pnlNoUsers.Visible = True
Else
pnlNoUsers.Visible = False
CustomerListLiteral.Text = strUsers & "</ul>"
End If
' Force an update refresh if necessary, but this shouldn't be needed
pnlCust.Update()
End Sub

Answer 3

Why you are using the function show_cust(). You can add the functionality in the button click action. because initially the panel is not visible. it need to to be visible while button click ccording to the condition. So add the functioality
`
If bHasUsers = False Then
pnlNoUsers.Visible = True
Return ""
End If
pnlNoUsers.Visible = False
Return strUsers & "</ul>"
on btnRefresh click event. It will work