Ajax Triggers for DropDownList don't fire

Troy Donavan · Dec 22, 2006

I'm trying to get a partial page (Ajax style) update when the selection of a
DropDownList changes. I'm not having much luck. I will continue plugging
away at the sample applications in hopes of finding some hints, but
meanwhile, if someone could point out to me what I am doing wrong, I would
appreciate it. Here is a page with three controls on it. They are for
selection of Country, State and Locality. The idea is that when one chooses
the country, the possible selections for state (region) would then update and
similarly for localities.

Let me know if you can spot my problem. Here is the code:

<%@ Page Language="VB" AutoEventWireup="true" CodeFile="Default.aspx.vb"
Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<div>

<asp:UpdatePanel ID="UPCountry" runat="server">
<ContentTemplate>

<asp

ropDownList ID="DDCountry" runat="server"
style="z-index: 100; left: 500px; position: absolute; top: 100px; width:
200px" OnLoad="DDCountry_Load">
</asp

ropDownList>

<asp

ropDownList style="Z-INDEX: 100; LEFT: 500px; WIDTH:
200px; POSITION: absolute; TOP: 130px" id="DDState" runat="server"
OnLoad="DDState_Load">
</asp

ropDownList>

<asp

ropDownList style="Z-INDEX: 100; LEFT: 500px; WIDTH:
200px; POSITION: absolute; TOP: 160px" id="DDLocality" runat="server"
OnLoad="DDLocality_Load">
</asp

ropDownList>
</ContentTemplate>
<triggers>
<asp:AsyncPostBackTrigger ControlID="DDState"
EventName="TextChanged"></asp:AsyncPostBackTrigger>
<asp:AsyncPostBackTrigger ControlID="DDCountry"
EventName="TextChanged"></asp:AsyncPostBackTrigger>
</triggers>
</asp:UpdatePanel>

</div>
</form>
</body>
</html>

technoGirl · Dec 24, 2006

Troy,

Shouldn't you be using OnSelectedIndexChanged =
DDCountry_SelectedIndexChanged for your drop downs??? Since you want a
ajax style functionality??
Tina

Walter Wang [MSFT] · Dec 25, 2006

Hi Troy,

As Tina pointed out, if you want to update second DropDownList when the
first one changes, you need to handle the first one's SelectedIndexChanged
event instead of the Load event. Also you need to set the first
DropDownList's AutoPostBack to true:

<asp:UpdatePanel ID="UPCountry" runat="server">
<ContentTemplate>
<asp

ropDownList ID="DDCountry" runat="server"
Style="z-index: 100; left: 500px;
position: absolute; top: 100px; width: 200px"
OnLoad="DDCountry_Load"
OnSelectedIndexChanged="DDCountry_SelectedIndexChanged" AutoPostBack="true">
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
</asp

ropDownList>

Protected Sub DDCountry_SelectedIndexChanged(ByVal sender As Object,
ByVal e As System.EventArgs)
DDState.Items.Clear()
Dim s As String = DDCountry.SelectedItem.Text
For i As Integer = 1 To 2
DDState.Items.Add(s + "_" + i.ToString())
Next
End Sub

Hope this helps.

Sincerely,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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Troy Donavan · Dec 27, 2006

AutoPostBack="true"

What a wonderful concept!!! Thank you very much!

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Ajax Triggers for DropDownList don't fire

Troy Donavan

technoGirl

Walter Wang [MSFT]

Troy Donavan

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