First Item in dropdownlist doesn't fire SelectedIndexChanged at all

Question

I have following simple code:

<%@ Page Language=\"C#\" AutoEventWireup=\"true\" CodeBehind=\"testForm.aspx.cs\" Inherits=\"Orbs.testForm\" %>

         


        

Answer 1

This is happening because you are setting the label to "???!!" every page event.

You need to modify your page load to detect f a Postback has not occured.

    protected void Page_Load(object sender, EventArgs e) {
        if(!IsPostBack)
        {
            label1.Text = "???!!";
        }
    }

Answer 2

This question covers all the possibilities better than other posts out there, so I'm adding this explicit answer. In my case @Edyn's comment worked, even though the original problem already has this:

Set ViewStateMode="Enabled" on the dropdown control itself.
I also set it on the page declaration at the top of the page, just in case.

This is .Net 4.0, so perhaps something was changed (but certainly not fixed nicely).

Answer 3

I had the same problem, but I solved it by calling onindexchanged function manually, like this:

ddl_SelectedIndexChanged(null, null);

I know this may not be the perfect way but it's working for me.

Answer 4

For Anyone still having the problem; I solved it in a different, yet easier way: Just add a dummy ListItem to the start of the DropDownList and set that item's Enabled property to false. i.e.

<asp:DropDownList ID="dropdown1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="dropdown1_SelectedIndexChanged" ViewStateMode="Enabled">
        <asp:ListItem Value="" Text="" Enabled="false" />
        <asp:ListItem Value="1" Text="Item 1" />
        <asp:ListItem Value="2" Text="Item 2" />
        <asp:ListItem Value="3" Text="Item 3" />
        <asp:ListItem Value="4" Text="Item 4" />
        <asp:ListItem Value="5" Text="Item 5" />
    </asp:DropDownList>

Answer 5

I solved the problem myself,

I read somewhere that turning off the ViewStateMode will cause DropDownListnot work properly. In my web application I had to turn off ViewStateMode to achieve some global task and turn it on case by case.

Somehow turning on ViewStateMode on DropDownList is not working, I even tried turning on ViewStateMode for page and master page but still DropDownList didn't work. it only worked when I turned on ViewStateMode in web.config.

As turning on ViewStateMode in web.config is not an option, I found and alternate solution. I'm including it here hoping it help someone.

• Add a HiddenField to your form.
• In Page_Load compare value of HiddenField with Request.Forms[DropDownList1.UniqueID]
• if they are different, call SelectedIndexChanged manually
• Set the value of HiddenField to value of Request.Forms[DropDownList1.UniqueID].

Answer 6

Had the same issue - SelectedIndexChanged doesn't fire when selecting the first option, My not clean solution was (not sure that was so smart but it work for me),

At the Page_Load I added the follow script:

if (!IsPostBack)
        {

            //bind data first time
        }
        else
        {
            int ddlSortByValue = int.Parse(ddlSortBy.SelectedValue);
            if (ddlSortByValue == 0)
            {
                ddlSortBy_SelectedIndexChanged(this, EventArgs.Empty);
            }

        }

That way I force the SelectedIndexChanged event to fire up