UpdatePanel AsyncPostbackTrigger not firing

Question

I've got a little problem, any help is appreciated.

Situation looks like this:

<asp:UpdatePanel ID="UP_Panel" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:DropDownList ID="ddlSwitch" runat="server" Width="250px" AutoPostback="true"
            OnSelectedIndexChanged="ddlSwitch_SelectedIndexChanged">

            <asp:ListItem Value="continent" Text="Continent"></asp:ListItem>
            <asp:ListItem Value="region" Text="Region"></asp:ListItem>
            <asp:ListItem Value="country" Text="Country"></asp:ListItem>

        </asp:DropDownList>

        <asp:UpdatePanel ID="UP_Switch" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                // Some content
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="ddlSwitch" EventName="SelectedIndexChanged" />
            </Triggers>
        </asp:UpdatePanel>
    </ContentTemplate>
</asp:UpdatePanel>

When ddlSwitch selected index change I want to update content inside UP_Switch, but SelectedIndexChanged event doesn't seem to fire. What am I doing wrong?

Thanks in advance!

Answer 1

I have just tested your code and seems to be working with some test modifications: ASPX

<asp:UpdatePanel ID="UP_Panel" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:DropDownList ID="ddlSwitch" runat="server" Width="250px" AutoPostback="true"
            OnSelectedIndexChanged="ddlSwitch_SelectedIndexChanged">

            <asp:ListItem Value="continent" Text="Continent"></asp:ListItem>
            <asp:ListItem Value="region" Text="Region"></asp:ListItem>
            <asp:ListItem Value="country" Text="Country"></asp:ListItem>

        </asp:DropDownList>

        <asp:UpdatePanel ID="UP_Switch" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                <asp:Literal ID="litUpSwitch" runat="server"></asp:Literal>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="ddlSwitch" EventName="SelectedIndexChanged" />
            </Triggers>
        </asp:UpdatePanel>
    </ContentTemplate>
</asp:UpdatePanel>

Code behind for ddlSwitch_SelectedIndexChanged:

protected void ddlSwitch_SelectedIndexChanged(object sender, EventArgs e)
{
    litUpSwitch.Text = "DDL Switch go activated";
}

Result: