DropDownList SelectedIndexChanged not firing

I have an issue with a DDL where my SelectedIndexChanged only gets fired when the second list item is selected (there are only 2 items in the list). The first item in the list is the default item and is set to selected. Also the list items are not bound via a datasource, they are already populated.

The DDL is wired up to the UpdatePanel as a Trigger. The DDL is also located outside the UpdatePanel - I tried having the DDL inside the UpdatePanel as well but the same issue comes up.

The Update does occur because I verified that the Page_Load fires when I switch between the two DDL items.

Any ideas?

The trick to this is to insert another record as the default selection of the DDL. I always insert a ListItem at run-time right after I bind the records to the DDL that tells the user to make a selection, for example 'Select State'. This solves two problems, it helps guide the user (let's face they need all the help they can get) and will force the selectedindexchanged event to fire like you want.

ddlState.Items.Insert(0,New ListItem("Select a State", 0))

Here is a Blog entry I made on the topic:

http://professionalaspnet.com/archive/2007/12/22/Cures-for-the-Common-Ailments-_2D00_-DropDownList.aspx

I was hoping that wasn't the fix but I guess I'll just have to work with it.

Thanks!

Have you set the property named "ChildrenAsTriggers" of the UpdatePanel to true?

DropDownList SelectedIndexChanged not fire (Autopostback - true!)

1<asp:DropDownList ID="SectionsDDL" runat="server" DataSourceID="SectionsObDS"2AutoPostBack="True" OnSelectedIndexChanged="SectionsDDL_SelectedIndexChanged"3DataTextField="titleName" DataValueField="id">4</asp:DropDownList>56<asp:UpdatePanel ID="UpdatePanel1" runat="server">7<ContentTemplate>8<asp:Panel ID="sectData" runat="server">9<asp:Label ID="tstlbl" runat="server" />10</asp:Panel>11</ContentTemplate>12<Triggers>13<asp:AsyncPostBackTrigger ControlID="sectionsDDL" EventName="SelectedIndexChanged" />14</Triggers>15</asp:UpdatePanel>

Everything is ok when I choose any item in DDL but first. When I choose first SelectedIndexChanged not fire.

I tried to find answer on forum and could not.

it sounds like your first item is selected when the dropdown loads so if you pick that answer the selected index never changes. Try adding an additional item called Not Selected or choos one or something along those lines as the first item in the list then everytime you should postback.

AjaxButter

Or you could change the SelectedIndex property to -1

DropDownList SelectedIndexChanged event not firing

I have a dropdown list that has many items in it - so in order to reduce viewstate size I have shut off viewstate for that control. But since doing so - the selectedindexchanged event is not firing (I guess because without view state the control does not know if there was a change in the selected value so it can't determine if it should fire the changed event.

Is there any way I can detect this change on the client and fire the selectedindexchanged event on the server?

thanks
Michael

May be you can try to bind the dropdown list in the Page_Init event handler.. Then you do not have to worry about viewstate.. Give it a try..

I tried that but that means everytime there is a postback (async or sync) it has to hit the db to re-populate that list.

I tried keeping track of the previously selected value in viewstate manually to detect a change and it detected the change correctly but I get an event validation error.

thanks
Michael

ok. I guess we are missing the pieces of information here... So you do not care about re-populating the list again? so what is going to be in the list.. after the postback is finished?

What event validation error you are talking about? Do you even care about the SelectIndexChanged event? Or you can simply explain more about what exactly you are trying to do?

I have a drop down list with autopostback = true and when an item is selected an update panel will refresh based on the selected item in the dropdown list. So I don't need to reload the dropdown list once it is loaded initially.

I actually solved the issue by looking at the event source in the forms collection and if it is the dropdown list - I know that the selected item was changed because the dropdown list won't do a postback unless the selected item was changed. I couldn't use the selecteditemchanged event because with the viewstate disabled - the server side does not know if the selected item changed.

I thought I had to store the previously selected item in viewstate to detect if a new item was selected but it turns out that a postback only occurs when the selected item is changed - which makes sense - the browser know that the item was changed - even though the server does not.

thanks
Michael

DropDownList causes a full page postback instead of only updating the UpdatePanel

I have a code for updating a DropDownList with items whenever another DropDownList triggers a SelectedIndexChanged event.

When I select an item in the DDLSelect dropdown, it causes a full page postback instead of just updating the UpdatePanel. This problem only occurs when I try to implement it in an existing project, and it works fine when if I try it in a new project.

I've updated my Web.config file to make my project compatible with AJAX, so I don't believe that's the problem.

I should add that I'm trying to use this inside an ascx UserControl file, so maybe there are known issues there.

Thanks in advance.

Please post the usercontrol code

OK, problem solved!

It was the Web.config after all. I had this line which caused the problem:

<

xhtmlConformancemode="Legacy"/>

I removed it and everything is fine.

Cheers.