Drop Down List (in Update Panel) causing FULL Post

Question

I have a problem with my AJAX and ASP.NET 3.5 :( Problem is really weird, as I'm using the same thing on different page and it works fine in there, but on this specific page, this is not working.

Here's what I have:

    <asp:UpdatePanel ID="upMain" runat="server" UpdateMode="Conditional" Visible="true" RenderMode="Inline">
                <ContentTemplate>
<asp:DropDownList ID="ddlNewService_PortTelco" runat="server" Width="250" CssClass="dropdown" AutoPostBack="true" OnSelectedIndexChanged="Provision_PortedTelcoChanged"></asp:DropDownList>
</ContentTemplate>
</asp:UpdatePanel>

On the way before the DropDown there is one DIV (html one), and then few asp:Panels. I do not understand why this is causing a FULL POST BACK ?!

Any ideas ? Thanks

Answer 1

How do you bind your DropDown? The code that you have provided works on my side with static items. Perhaps it is something in the other controls that is causing the problem.

I have noticed that your UpdatePanel has its UpdateMode property set to conditional, however you haven't defined any triggers.You can try to explicitly set that the update panel should perform async postback when your dropdown triggers its selectedIndexChanged event. You can use something like the following markup:

<asp:UpdatePanel ID="upMain" runat="server" UpdateMode="Conditional" Visible="true"
    RenderMode="Inline">
    <ContentTemplate>
        <asp:DropDownList ID="ddlNewService_PortTelco" runat="server" Width="250" 
            AutoPostBack="true" OnSelectedIndexChanged="Provision_PortedTelcoChanged">
        </asp:DropDownList>
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="ddlNewService_PortTelco" EventName="SelectedIndexChanged" />
    </Triggers>
</asp:UpdatePanel>

Answer 2

Me having the same problem...

CHECK your WEB.CONFIG

<xhtmlConformance mode="Legacy"/>

for this line.. and JUST REMOVE IT!!

Worked for me. Thanks http://andrew-murphy.co.uk/?p=152

Answer 3

Setting the AutoPostBack attribute to true should be enough to cause a partial postback but it's not what happens and a full postback is triggered instead as you correctly described.

The following workaround works for me:

1. Drop the AutoPostBack attribute.
2. Trigger the postback using the "onchange" client side event.

This is how the original DropDownList should look like:

<asp:DropDownList ID="ddlNewService_PortTelco" runat="server" Width="250" CssClass="dropdown" OnChange="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions(this.name, '', true, '', '', false, true))" OnSelectedIndexChanged="Provision_PortedTelcoChanged"></asp:DropDownList>

For more details regarding the WebForm_PostBackOptions parameters see below:

function WebForm_PostBackOptions(eventTarget, eventArgument, validation, validationGroup, actionUrl, trackFocus, clientSubmit)

http://msdn.microsoft.com/en-us/library/system.web.ui.postbackoptions_members(v=VS.90).aspx

Answer 4

Set AutoID value to ClientIDMode property. It worked for me. I have had different behaviour in different browsers (i.e. Google chrome and Firefox).

Answer 5

One alternative to fix this issue is:

Declare the library

using AjaxControlToolkit;

Then you can do something on these lines

private void InitControl()
{        
            //FIX - DROP DOWN
            ToolkitScriptManager scrManager = (ToolkitScriptManager)Page.Master.Controls[0].Controls[0].FindControl("manScript");
            scrManager.RegisterAsyncPostBackControl(ddlNewService_PortTelco);
}

Answer 6

You have your drop down list with an AutoPostBack set to true. That's why you have it post back instead of AsyncPostBack, if that is what you wanted.

Remove the AutoPostBack=true from the dropdownlist and set an Async trigger for your UpdatePanel set to the dropdownlist and its eventname="SelectedIndexChanged"