ASP.NET panel does not update when last item gets deleted - asp.net

Question

I am sure that I am missing something really obvious here, but I just can't see it.
I have an update panel with a datalist inside it. Each item of the datalist has a delete button with which I issue the Delete command for the item.
Deletion is a two part process: I first pop up a modal dialogue from codebehind to ask for confirmation, like so:
/// <summary>
/// Manager delete command
/// </summary>
protected void dlKeywordsManager_DeleteCommand(object source, DataListCommandEventArgs e)
{
//Get the subject ID
int keywordID = (int)dlKeywordsManager.DataKeys[e.Item.ItemIndex];
//Remember the keyword ID on the modal popup
hfKeywordID.Value = keywordID.ToString();
btnConfirmationPopupOK.CommandArgument = "Delete";
lblConfirmationPopupMessage.Text = "キーワード「" + e.CommandArgument.ToString() + "」を本当に削除しますか？";
mpConfirmationPopup.Show();
dlKeywordsManager.DataBind();
udpKeywordsManager.Update();
}
This modal popup is also within the update panel so that I can get the label text values refreshed on partial postback.
When the use presses the OK button of the popup I go on to execute:
protected void btnConfirmationPopupOK_Click(object source, EventArgs e)
{
int keywordID = int.Parse(hfKeywordID.Value);
KeywordBLLOperation operationResult;
switch (((Button)source).CommandArgument)
{
case "Delete":
operationResult = keywordsAPI.DeleteKeyword(keywordID);
switch (operationResult.Result)
{
case KeywordBLLOperationResult.Deleted:
lnlNotificationsPopupMessage.Text = "キーワード「" + operationResult.KeywordName + "」を削除しました。";
break;
case KeywordBLLOperationResult.Failed:
lnlNotificationsPopupMessage.Text = "キーワード「" + operationResult.KeywordName + "」の削除に失敗しました。アドミニストレーターにお伝えください。";
break;
}
break;
}
mpNotificationPopup.Show();
dlKeywordsManager.DataBind();
udpKeywordsManager.Update();
}
I have remove a few non-essential lines here for brevity.
And here is the aspx markup to go with the code:
<asp:UpdatePanel ID="udpKeywordsManager" runat="server" Visible="true" UpdateMode="Conditional" >
<ContentTemplate>
<div class="keywordsManagerHeader">
<%--DISPLAY STATISTICS--%>
<asp:CheckBox ID="chkShowUsageStatistics" runat="server" Text="参照回数を表示する" AutoPostBack="true" OnCheckedChanged="chkShowUsageStatistics_CheckedChanged" CssClass="keywordsManagerCheckBoxes" TextAlign="Left" />
<%--DISPLAY ORDER--%>
<span class="keywordsManagerLabel" >並べ替え</span>
<asp:DropDownList ID="ddlKeywordsOrder" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlKeywordsOrder_SelectedIndexChanged" >
<asp:ListItem Text="なし" Value="None" />
<asp:ListItem Text="科目名" Value="Name" />
<asp:ListItem Text="参照回数" Value="Frequency" />
</asp:DropDownList>
<asp:RadioButtonList ID="rdlOrder" runat="server" AutoPostBack="true" RepeatLayout="Flow" RepeatDirection="Horizontal" CssClass="keywordsManagerRadioButtons" Enabled="false" >
<asp:ListItem Text="昇順" Value="Ascending" />
<asp:ListItem Text="降順" Value="Descending" />
</asp:RadioButtonList>
<%--UPDATE PROGRESS INDICATOR--%>
<span style="position: absolute;">
<asp:UpdateProgress ID="udpSubjectsManagerUpdateProgress" AssociatedUpdatePanelID="udpKeywordsManager" runat="server" DisplayAfter="500" DynamicLayout="False" >
<ProgressTemplate>
<img class="updateProgressIndicator" src="~/Library_Images/Animations/ajax_loading.gif" alt="" runat="server" />
</ProgressTemplate>
</asp:UpdateProgress>
</span>
</div>
<div class="keywordsManagerContainer">
<%--SUBJECTS DATALIST--%>
<asp:DataList ID="dlKeywordsManager" runat="server" DataKeyField="Keyword_ID" DataSourceID="dsBookKeywords" RepeatDirection="Horizontal"
OnItemDataBound="dlKeywordsManager_ItemDataBound" OnDeleteCommand="dlKeywordsManager_DeleteCommand" OnUpdateCommand="dlKeywordsManager_UpdateCommand" OnPreRender="dlKeywordsManager_PreRender" >
<ItemTemplate>
<span id="KeywordInfo" class="keywordsManagerItem" runat="server">
<asp:Label ID="Subject_NameLabel" runat="server" Text='<%# Eval("Keyword_Name") %>' />
<asp:Label ID="Subject_FrequencyLabel" runat="server" Text='<%# " (" + Eval("Frequency") + ")" %>' Visible="false" />
</span>
<%--HOVER MENU PANEL--%>
<asp:Panel ID="pnlKeywordContextMenu" runat="server" CssClass="keywordsManagerPopupMenuOverall">
<div class="keywordsManagerPopupMenuRow" >
<span class="keywordsManagerLabel">科目「</span>
<asp:Label ID="pnlSubjectContextMenu_Subject_NameLabel" runat="server" Text='<%# Eval("Keyword_Name") %>' />
<span class="keywordsManagerLabel">」を参照している文書数：</span>
<asp:Label ID="pnlSubjectContextMenu_Subject_FrequencyLabel" runat="server" Text='<%# Eval("Frequency") %>' />
</div>
<div ID="Book_ISO_NumbersList" class="keywordsManagerBookISONumbersList" runat="server" visible='<%# (string.IsNullOrEmpty(Eval("Book_ISO_Numbers").ToString())) ? bool.Parse("false") : bool.Parse("true") %>' >
<span class="keywordsManagerLabel">文書：</span>
<asp:Label ID="Book_ISO_Numbers_Label" runat="server" Text='<%# Eval("Book_ISO_Numbers") %>' />
</div>
<div class="keywordsManagerPopupMenuSeparator"></div>
<div class="keywordsManagerPopupMenuRow" >
<asp:TextBox ID="Keyword_NameTextBox" runat="server" Text='<%# Eval("Keyword_Name") %>' CssClass="keywordsManagerPopupMenuInput" />
<asp:Button ID="btnEdit" runat="server" Text="編集" CssClass="buttonShortBottom" CommandName="Update" CausesValidation="true" CommandArgument='<%# Eval("Keyword_Name") %>' />
<asp:Button ID="btnDelete" runat="server" Text="削除" CssClass="buttonShort" CommandName="Delete" CommandArgument='<%# Eval("Keyword_Name") %>' />
</div>
</asp:Panel>
<%--HOVER MENU EXTENDER--%>
<asp:HoverMenuExtender ID="hmeKeywordContextMenu" runat="server" TargetControlID="KeywordInfo" PopupControlID="pnlKeywordContextMenu" PopDelay="100" PopupPosition="Right" HoverDelay="100" />
</ItemTemplate>
<SeparatorTemplate>
<span class="keywordsManagerItemSeparator"></span>
</SeparatorTemplate>
</asp:DataList>
</div>
<%--MODAL POPUPS--%>
<%--CONFIRMATION POPUP--%>
<asp:Panel ID="pnlConfirmationsPopup" runat="server" CssClass="modalNotificationOverall" >
<div class="modalNotificationRow">
<asp:Label ID="lblConfirmationPopupMessage" runat="server" Text="" />
</div>
<div class="modalNotificationRow">
<asp:Button ID="btnConfirmationPopupOK" runat="server" Text="はい" CssClass="buttonMediumLong" OnClick="btnConfirmationPopupOK_Click" />
<asp:Button ID="btnConfirmationPopupCancel" runat="server" Text="いいえ" CssClass="buttonMediumLong" />
</div>
<asp:HiddenField ID="hfKeywordID" runat="server" />
<asp:HiddenField ID="hfNewKeywordName" runat="server" />
</asp:Panel>
<%--NOTIFICATION POPUP--%>
<asp:Panel ID="pnlNotificationsPopup" runat="server" CssClass="modalNotificationOverall" >
<div class="modalNotificationRow">
<asp:Label ID="lnlNotificationsPopupMessage" runat="server" Text="" />
</div>
<div class="modalNotificationRow">
<asp:Button ID="btnNotificationsPopupOK" runat="server" Text="OK" CssClass="buttonMediumLong" />
</div>
</asp:Panel>
<%--MODAL POPUP ANCHORS AND MODULES--%>
<%--DELETE CONFIRMATION--%>
<asp:Label ID="lblConfirmationPopupAnchor" runat="server" Text="" />
<asp:ModalPopupExtender ID="mpConfirmationPopup" runat="server" TargetControlID="lblConfirmationPopupAnchor" PopupControlID="pnlConfirmationsPopup" BackgroundCssClass="modalNotificationBackground" CancelControlID="btnConfirmationPopupCancel" />
<asp:Label ID="lblNotificationPopupAnchor" runat="server" Text="" />
<asp:ModalPopupExtender ID="mpNotificationPopup" runat="server" TargetControlID="lblNotificationPopupAnchor" PopupControlID="pnlNotificationsPopup" BackgroundCssClass="modalNotificationBackground" CancelControlID="btnNotificationsPopupOK" />
</ContentTemplate>
There is a lot of markup in there. The structure is as follows: I have a header section with dropdownlist, radiobuttonlist etc. which allows me to specify the sorting of the data (data comes from an object datasource)
The I have the datalist with items. Each item has a hovermenuextender in which I have the buttons to issue the edit and delete comamnds.
The modal popups are also inside the update panel, but outside the datalist, so that they can be updated as required.
My problem is that this works fine as long as the item I delete is not the last item left in the Datalist. If it is the last item the last popup (mpNotificationPopup) doesn't show.
The code executes all the way through, so the lack of items must cause the upadte panel (udpKeywordsManager) not to update?
Any help as to how to get the datalist to update in this case would be most welcome.
Thanks in advance.

Answer 1

Answering my own question. After painfully rebuilding the whole thing I realised that I was setting the visibility of the update panel to false in the OnPreRender event of the datalist when there were no items left. This basically switched off the update panel half-way through refreshing, so the page didn't refresh when the last element was deleted.
Have sorted it by putting a panel in the update panel which contains all the elements inside it except the "no info available" label and just toggle the visibility of that. Apologies for the stupid question, I guess I was having a stupid moment when I wrote this code...

Answer 2

You should show us the aspx-markup as well, but maybe you've used a ModalPopupExtender inside of your UpdatePanel. Try to move the div/Panel that has the ID of the ModalPopupExtender's PopupControlID property outside of your UpdatePanel.
You only have to nest the UpdatePanel inside of the Popup-Control and not around it.
I hope following makes it clearer:
Instead of doing it this way:
<UpdatePanel>
<DataList>
</DataList>
<ModalPopupExtender>
</ModalPopupExtender>
</UpdatePanel>
You should do it this way:
<ModalPopupExtender>
<UpdatePanel>
<DataList>
</DataList>
</UpdatePanel>
<ModalPopupExtender>