VB.Net "logger" asp:Table and asp:UpdatePanel dynamic asynchronous update - asp.net

Question

I am writing a web page in ASP.Net. Presently, I have an asp:Table that I am using as a sort of "log" for processing output. The idea is that the user selects several files and clicks a button, and each file is "processed" with the log showing what is happening. Processing occurs asynchronously.
Here is the relevant processing segment:
Protected Sub DoAsyncWork()
Dim count = 0
For Each row As GridViewRow In gvList.Rows
count = count + 1
If CType(row.FindControl("cbImport"), System.Web.UI.WebControls.CheckBox).Checked Then
push_to_log("")
push_to_log("Updating Active Projects +" + HttpUtility.HtmlDecode(row.Cells(1).Text).ToString.Substring(0, 30) + "...")
Dim xp(3) As Object
xp(0) = HttpUtility.HtmlDecode(row.Cells(0).Text)
xp(1) = HttpUtility.HtmlDecode(row.Cells(1).Text)
xp(2) = HttpUtility.HtmlDecode(row.Cells(2).Text)
xp(3) = 0
'oDC.UpdateData("Import_P3e_Project ", xp)
If (xp(3) <> 0) Then
push_to_log("Success: " + xp(3).ToString + " have been updated")
Else
push_to_log("Failure: " + xp(3).ToString + " activities updated")
End If
End If
Next
push_to_log("")
push_to_log("Import Complete!")
End Sub
This is how I am calling the process worker function:
Protected Sub button_Import(sender As Object, e As EventArgs) Handles btnImport.Click
Dim t As New Thread(New ThreadStart(AddressOf DoAsyncWork))
t.Priority = Threading.ThreadPriority.Normal
t.Start()
push_to_log("Start Import")
End Sub
The way I am appending things to the log is by dynamically creating rows and cells, then adding them to my table. Here is the relevant subroutine:
Protected Sub push_to_log(ByVal str As String)
Dim newRow As TableRow = New TableRow
Dim newCell As TableCell = New TableCell
logArrayList.Add(str)
Me.ViewState.Add("arrayListInViewState", logArrayList)
newCell.Text = str
newCell.Style("Color") = "White"
newCell.ID = "cell" + (logArrayList.Count - 1).ToString
newRow.ID = "row" + (logArrayList.Count - 1).ToString
newRow.Cells.Add(newCell)
logTable.Rows.Add(newRow)
HiddenButton_Click(HiddenButton, New EventArgs())
'UpdateLogPanel.Update()
'UpdateLogPanel.Focus()
End Sub
I've got the log persisting correctly by using the ViewState to store my arraylist of data and recreating the log on postbacks. The relevant markup for my log looks like this:
<asp:UpdatePanel ID="UpdateLogPanel" UpdateMode="Conditional" runat="server">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="HiddenButton" />
</Triggers>
<ContentTemplate>
<div ID="Div1" class="DefinitionPanel" style="text-align:left;height:200px;overflow:hidden;" runat="server">
<span style="display:inline-block; width:100px;"></span>
<div class="scrollingtable">
<div>
<div id="viewContainer">
<asp:table id="logTable" runat="server" enableviewstate="false">
</asp:table>
</div>
</div>
</div>
</div>
<asp:Button ID="HiddenButton" runat="server" style="display:none;" />
</ContentTemplate>
</asp:UpdatePanel>
I am trying to make my asp:Table update every time a message is posted to it. I thought that enabling partial postbacks and using an UpdatePanel would be the correct solution, but my log still does not output anything until the entire process has completed.
After I add a message to my asp:Table/log, I tried calling
UpdateLogPanel.Update()
which didn't seem to make a difference. Finally I tried adding the asp:AsyncPostBackTrigger and hidden button with the hope that it would fix things but it doesn't seem to. Here is what the hiddenButton event looks like:
Protected Sub HiddenButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles HiddenButton.Click
UpdateLogPanel.Visible = True
End Sub
Any guidance on how to make my log re-render itself when I add a message to it would be highly regarded.

Answer 1

I chose to implement using pooling instead of an asynchronous method.
I still use an asp:UpdatePanel. Instead of a table inside of the UpdatePanel, I am now using a gridview, and a timer. When the timer fires, I rebind the gridview, thereby showing any new contents
The key components to making this work:
Square things away with the parent update panel and master page:
Private Sub Page_Init(sender As Object, e As System.EventArgs) Handles Me.Init
'set reference to master site page
mstr = CType(Master, Site)
'setup partial rendering so Log can update asynchronously
scriptManager = CType(mstr.FindControl("ScriptManager1"), ScriptManager)
scriptManager.EnablePartialRendering = True
scriptManager.AsyncPostBackTimeout = 28800
CType(mstr.FindControl("UpdatePanel1"), UpdatePanel).UpdateMode = UpdatePanelUpdateMode.Conditional
CType(mstr.FindControl("UpdatePanel1"), UpdatePanel).ChildrenAsTriggers = False
End Sub
The mark-up for the UpdatePanel looks like
<asp:UpdatePanel ID="UpdateLogPanel" UpdateMode="Conditional"
RenderMode="Inline" ChildrenAsTriggers="false" runat="server">
<ContentTemplate>
<%--The Gridview and other Hidden Fields--%>
<asp:Timer ID="myTimer" OnTick="timer_tick" runat="server" Interval="1000" Enabled="false"/>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="myTimer" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
Triggering the logging mechanism is done simply by setting
myTimer.Enabled = True
The timer_tick event looks like
Public Sub timer_tick(ByVal sender As Object, ByVal e As EventArgs)
generate_log()
//other logging logic (increment counters, "timeout" mechanism)
UpdateLogPanel.Update()
End Sub