Dropdown in listview SelectedIndexChanged doesn't work first time but does after - asp.net

Question

I've searched high and low, I can't seem to find out what's happening with this. I've simplified the code, but I really have taken it back to as basic as this and still have the same problem.
I have a drop down list in a a repeater (in a Web Form with master page):
<asp:DropDownList ID="TicketQuantityDDL" runat="server" CssClass="qtyddl" AutoPostBack="true" OnSelectedIndexChanged="TicketQuantityDDL_SelectedIndexChanged" CausesValidation="false" SelectedIndex='<%# CInt(Eval("Quantity")) - 1%>'>
<asp:ListItem Value="1">1</asp:ListItem>
<asp:ListItem Value="2">2</asp:ListItem>
<asp:ListItem Value="3">3</asp:ListItem>
<asp:ListItem Value="4">4</asp:ListItem>
<asp:ListItem Value="5">5</asp:ListItem>
<asp:ListItem Value="6">6</asp:ListItem>
</asp:DropDownList>
Handler
Protected Sub TicketQuantityDDL_SelectedIndexChanged(sender As Object, e As EventArgs)
myLiteral.text = "Selected Index Changed handled..."
End Sub
The first time the page is loaded if I change the DDL the the page is posted back - the selected index change handler is NOT fired (I've stepped through the code, page.ispostback is true). Every time after the handler works unless the page is full reloaded.
Things I've tried:
Manually adding a handler OnItemCreated
Manually adding a handler OnItemDataBound
Manually registering the control for async postback with scriptmanager
Using OnClientSelectedIndexChanged to trigger postback from the client
Removing AutoPostBack and all of the above again...
I've used Page.Request.Params("__EVENTTARGET") to verify that when the partial postback is fired that the control is the drop down.
Even though viewstate is enabled I've tried specifying this for the control and the page directly.
Disabling validation.
I've tried not binding the value of the drop down and just leaving it
as is with no selected value and then manually setting the initial
selected value - no dice.
Tried removing update panel, same issue.
Things that are DEFINITELY not happening here.
I'm not rebinding on post back if not page.ispostback... databind...
I'm not selecting the same value/first item in the drop down
This isn't an auto ID problem, the controls ID stay the same through postbacks.
I'm not doing anything funky other than binding the repeater to a list of objects.
Why isn't the handler firing the first time? After the first time everything works exactly as intended.
Update
I've replicated the exact same behaviour in a list view. Due to time constraints I've used another approach but I'd really like to know how to fix this or at least know why it doesn't work.
Update 2
I've tested the functionality with a bog standard web form and it functions correctly. Something is up with this being in a contentplaceholder from a masterpage, the script manager or update panel. It's as if the event handler for the dropdown is only registered after the first post back, I've tried registering the handler in DataBound and also in the page LoadComplete events, the same thing still happens.
Update 3
I've since changed it to a list view, I'm having the exact same issue though.
This is on a web form with master page, the master page contains the script manager, the list view is in an update panel, although I've tried removing this and I still have the same issue. I've not included the onselectedindexchanged code, I've made it as simple as changing the text of a literal - doesn't work first post back, does the second.
I had originally specified the list items manually but have changed this to programatically at itemDataBound, still no difference.
As I stated above when I check which control caused the postback it's definitely the ddl, it just doesn't fire selectindexchanged the first time. I've also tried specifying the OnSelectedIndexChange in the control itself, still no dice.
Page load ,bind, list view and on item created code.
Page Load
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
Dim _Basket = SessionHandler.getSessionObject(SessionHandler.SessionObjects.Basket)
If _Basket Is Nothing OrElse DirectCast(_Basket, BasketContainer).BasketItemList.Count = 0 Then
BasketSectionContainer.Visible = False
alertLiteral.Text = AlertGenerator.GetAlertHTML("No Items in Basket", "There are no items in your basket, please use the menu above to navigate the site.", AlertGenerator.AlertType.warning)
If _Basket IsNot Nothing Then SessionHandler.removeSessionObject(SessionHandler.SessionObjects.Basket)
Exit Sub
Else
Dim lBasket = DirectCast(_Basket, BasketContainer)
BindBasket(lBasket)
End If
End If
End Sub
Bind
Private Sub BindBasket(lBasket As BasketContainer)
basketListView.DataSource = lBasket.BasketItems
basketListView.DataBind()
bindTotals(lBasket) 'This just sets text of literals on the page outside of the listview
If lBasket.Postage Then
PostageDDL.visible = True 'This is outside of the list view also
End If
End Sub
Item Created
Private Sub basketListView_ItemCreated(sender As Object, e As ListViewItemEventArgs) Handles basketListView.ItemCreated
Dim QtyDDL As DropDownList = DirectCast(e.Item.FindControl("TicketQuantityDDL"), DropDownList)
AddHandler QtyDDL.SelectedIndexChanged, AddressOf TicketQuantityDDL_SelectedIndexChanged
End Sub
_Item Data Bound _
Private Sub basketListView_ItemDataBound(sender As Object, e As ListViewItemEventArgs) Handles basketListView.ItemDataBound
Dim data As BasketItem = DirectCast(e.Item.DataItem, BasketItem)
Dim QtyDDL As DropDownList = DirectCast(e.Item.FindControl("TicketQuantityDDL"), DropDownList)
For i As Integer = 1 To 6
QtyDDL.Items.Add(New ListItem(i.ToString, i.ToString))
Next
QtyDDL.DataTextField = data.BasketItemID.ToString 'no command arg for DDL so using this, I've tested without, doesn't make a difference.
Select Case data.BasketType
Case BasketInfo.BasketItemType.DiscountedTickets, BasketInfo.BasketItemType.Tickets, BasketInfo.BasketItemType.Goods
'tickets and goods...
QtyDDL.Items.FindByValue(data.Quantity.ToString).Selected = True
Case Else
'non ticket or goods type, disable quantity selection
QtyDDL.Items.FindByValue("1").Selected = True
QtyDDL.Enabled = False
End Select
End Sub
_List View _
<asp:ListView ID="basketListView" runat="server">
<LayoutTemplate>
<table class="cart-table responsive-table">
<tr>
<th>Item</th>
<th>Description</th>
<th>Price</th>
<th>Quantity</th>
<th>Total</th>
<th></th>
</tr>
<asp:PlaceHolder ID="itemPlaceholder" runat="server" />
</table>
<table class="cart-table bottom">
<tr>
<th>
<asp:Button ID="ApplyDiscountCodeButton" runat="server" CssClass="button color pull-right" Text="Apply Code" />
<asp:TextBox ID="DiscountCodeTextBox" runat="server" CssClass="discount-tb pull-right" />
</th>
</tr>
</table>
<div class="clearfix"></div>
</LayoutTemplate>
<ItemTemplate>
<tr>
<td>
<img src="/images/shows/<%# Eval("imageURL")%>.jpg" alt="<%#Eval("BasketItemTitle")%>" class="basketimg" /></td>
<td class="cart-title">
<%#Eval("BasketItemTitle")%>
<br />
<%# String.Format("{0:dddd} {1} {0:MMMM yyyy} | {0:HH:mm}", Eval("PerformanceStarts"), Eval("OrdinalDay"))%>
<br />
<%# Eval("VenueTitle")%>
</td>
<td>
<%#Eval("PriceBandType")%>
<br />
# <%# String.Format("{0:c}", Eval("PriceBandValue"))%>
</td>
<td>
<asp:DropDownList ID="TicketQuantityDDL" runat="server" CssClass="qtyddl" AutoPostBack="true" ClientIDMode="Static" />
</td>
<td class="cart-total"><%#String.Format("{0:c}", Eval("BasketItemTotalValue"))%></td>
<td>
<asp:LinkButton ID="RemoveLinkBtn" runat="server" CssClass="cart-remove" CommandName="RemoveBasketItem" CommandArgument='<%#Eval("BasketItemID")%>' />
</td>
</tr>
</ItemTemplate>
</asp:ListView>

Answer 1

Since the Dropdown in inside the repeater, you can try the following Option instead.
Add OnItemCommand to the repeater. This should definitely Trigger the Event on selection Change in the Dropdown. Then in the OnItemCommand you Need to cast the Sender to DropDownList to be able get the selected value of the dropdown

Answer 2

You have to register the dropdown list event like this.
protected virtual void OnRepeaterItemCreated(object sender, RepeaterItemEventArgs e)
{
DropDownList dropdown = (DropDownList)e.Item.FindControl("TicketQuantityDDL");
dropdown.SelectedIndexChanged += TicketQuantityDDL_SelectedIndexChanged;
}
And also add this piece of code in your repeater.
OnItemCreated="OnRepeaterItemCreated"
And then you can do the selected index changed event like this.
protected void TicketQuantityDDL_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList mydropdownlist = (DropDownList)sender;
Response.Write(mydropdownlist.SelectedValue);
}

Answer 3

protected void dropdownlist1_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList ddlListFind = (DropDownList)sender;
ListViewItem item1 = (ListViewItem)ddlListFind.NamingContainer;
DropDownList getDDLList = (DropDownList)item1.FindControl("dropdownlist1");
Label lblMessage = (Label)item1.FindControl("lblMsg");
lblMessage.Visible = true; lblMessage.Text = "dropDown text is : " + getDDLList.SelectedItem.Text + " and value is : " + getDDLList.SelectedItem.Value;
}