ModalPopup, UpdatePanel, Javascript "Object expected" Error with Internet Explorer

New information! The problem I describe below occurs only with Microsoft Internet Explorer. All others that I tested behaved as they should. Even Microsoft Edge handled it just fine. A lot of people use IE, so perhaps somebody knows a way to deal with the following problem:

A page in my asp.net web app has a modal popup which contains a listbox that must be populated on the fly. The page contains a treeview control; right clicking a node on the treeview calls up a context menu; and if the user clicks on "Add Pretask", the popup form appears, listing items which vary depending upon which node was clicked.

The listbox is contained within an UpdatePanel which was inserted so that the list could be populated without reposting the entire page. I developed this popup, tested it, and it appeared to be working properly. I was patting myself on the back for a job well done when I happened to press a key on the computer keyboard. The app crashed with the following error message:

"Unhandled exception at line 1010, column 1 in http://localhost:55109/PPM/ScriptResource.axd?d=8GNeJYrV145FFZwe3zZTQTMdSqo5ZWiNHMcMCdX41b_dp65omt53usfcChKlDkhIbPdehfLSEKVkXbwQruOiDLDfxhVjDQZOQZDVfHxfkhrBY3rHZVHxg2I6VQGIFSKL2AhGUprc1gW7X0t1_Q79OAckMdH-JliDUkID4lzcsT8Bfkxn0&t=1e478eba

0x800a138f - JavaScript runtime error: Object expected"

This behavior is consistent. The popup will not tolerate any key strokes.

I have been wrestling with this problem for days. Thank you for any help you can offer.

Here is the relevant markup:

     <a href="#" style="display:none;" onclick="javascript:return false" id="hidlinkAddPretask" 
runat="server">dummy</a>

<cc1:ModalPopupExtender ID="mpePretask" runat="server"  PopupControlID="pnlPretask" TargetControlID="hidlinkAddPretask"
     CancelControlID="btnCancelPretask" ></cc1:ModalPopupExtender>

<asp:Panel ID="pnlPretask" runat="server" CssClass="popupPanel" Width="40%">

    <asp:UpdatePanel ID="updPretask" runat="server" ChildrenAsTriggers="false" UpdateMode="Conditional">
       <ContentTemplate>

    <!-- Panel within pnlPretask contains list of selected. -->
     <asp:panel runat="server" ID="pnlPretaskList" Visible="false">
        <asp:BulletedList ID="blPretasks" runat="server">
        </asp:BulletedList>
    </asp:panel>


            <asp:HiddenField runat="server" ID="hidPostTaskID" Visible="true" />

            Before <b>"<asp:Label ID="lblAddPretask" runat="server"></asp:Label>"</b> can be completed, I must:
            <br /><br />

           <asp:ListBox ID="lboxPretask" runat="server" Width="80%" Height="200px"
                 ToolTip="Select one or more tasks that must be completed before..." AutoPostBack="false"
                 SelectionMode="Multiple">
          </asp:ListBox>

        </ContentTemplate>
    </asp:UpdatePanel>

   <br /><br />
    <asp:UpdateProgress ID="UpdateProgress4" runat="server" DisplayAfter="0">
        <ProgressTemplate>
            <img src="images/progress.gif" alt="" />&nbsp;Updating...</ProgressTemplate>
    </asp:UpdateProgress>

    <asp:Label runat="server" ID="lblErrPretask" Font-Bold="True" ForeColor="Red" />
    <br />
    <asp:Button ID="btnAddAnotherPretask" runat="server" Text="Save and Add Another" />
    <asp:Button ID="btnSavePretask" runat="server" Text="Save" />
    <asp:Button ID="btnCancelPretask" runat="server" Text="Cancel"   />
</asp:Panel>

The popup is launched from the server by this vb code:

        Dim ID As String = e.NodeClicked.Attributes("TaskID").ToString
        'Repopulate listbox
        PretaskSelectList(ID)
        updPretask.Update()
        mpePretask.Show()

And this vb routine populates the listbox:

Private Sub PretaskSelectList(ByVal TaskID As Integer)
    Dim strConn As String = ConfigurationManager.ConnectionStrings("PPMConnectionString").ConnectionString
    Dim cnn As SqlConnection = New SqlConnection(strConn)

    cnn.Open()

    'Get two result sets from uspPretaskPickList
    Dim sql As String = "execute dbo.uspPretaskPickList " & TaskID.ToString

    Dim cmd As SqlCommand = New SqlCommand(sql, cnn)

    'Result set #1 - Tasks from current Goal
    Dim rdr As SqlDataReader = cmd.ExecuteReader()
    Dim Itm As ListItem

    With lboxPretask
        .Enabled = True

        .Items.Clear()

        'Add a default item, #0
        Itm = New ListItem("ADD NEW TASK", "0")
        Itm.Attributes.Add("Style", "Font-Weight:Bold")
        .Items.Add(Itm)

        'Insert a separator if data reader has any records
        Dim separator As New ListItem("-------------------------", "")
        separator.Attributes.Add("disabled", "true")

        If rdr.HasRows Then
            .Items.Add(separator)
        End If

        'Add each member of 1st result set, using lboxPretask.Items.Add(New ListItem(TaskName, TaskID))
        Do While rdr.Read
            Itm = New ListItem(rdr("TaskName"), rdr("TaskID").ToString)
            'Each item should be Bold. 
            Itm.Attributes.Add("Style", "Font-Weight:Bold")
            .Items.Add(Itm)
        Loop

        'Add dividing line, Pretask.Items.Add("------------", "-1")
        separator.Attributes.Add("disabled", "true")
        .Items.Add(separator)

        'Results set #2 - Tasks from other or no goal
        rdr.NextResult()

        'Add each member of 2nd result set, using lboxPretask.Items.Add(New ListItem(TaskName, TaskID))
        Do While rdr.Read
            Itm = New ListItem(rdr("TaskName"), rdr("TaskID").ToString)
            .Items.Add(Itm)
        Loop

    End With

    rdr.Close()
    cnn.Close()

    rdr = Nothing
    cnn = Nothing

    lboxPretask.ClearSelection()

End Sub

Thanks again for any insights you can provide.

Looks like your JS file is not getting referenced properly on your page.

You can fix the issue by referencing it like below.

<script type="text/javascript" src=<%# ResolveUrl("http://code.jquery.com/jquery-latest.min.js") %> ></script>

Reference:

0x800a138f - Microsoft JScript runtime error: Object expected