[DotNetDevelopment] Update BgColor with ASP.NET AJAX

[Berk]

I'm developing an ASP.NET AJAX Application which sending multiple
mails. Mail list is collected in a repeater and Repeater'a each
RepeaterItem's backcolor must change after mail send. My code is
below, it doesn't change the bgcolor regardless of the fact that mail
sent. Any help will be appreciated.

   1.
              <asp:ScriptManager ID="ScriptManager1" runat="server" />
   2.
              <asp:Timer runat="server" id="UpdateTimer"
interval="2000" ontick="UpdateTimer_Tick" />
   3.
              <asp:UpdatePanel runat="server" id="TimedPanel"
updatemode="Conditional">
   4.
                  <Triggers>
   5.
                      <asp:AsyncPostBackTrigger
controlid="UpdateTimer" eventname="Tick" />
   6.
                  </Triggers>
   7.
                  <ContentTemplate>
   8.

   9.
                  <asp:Repeater ID="myRepeater" runat="server"
onitemdatabound="myRepeater_ItemDataBound" >
  10.
                  <HeaderTemplate>
  11.
                    <table>
  12.
                    <tr>
  13.
                       <th>Name</th>
  14.
                       <th>Description</th>
  15.
                    </tr>
  16.
                </HeaderTemplate>
  17.
                <ItemTemplate>
  18.

  19.
                <tr id="tr" runat="server" style="background-
color:Red">
  20.
                    <td>
  21.
                      <asp:Label runat="server" ID="Label1"
  22.
                         text='<%# Eval("Name") %>' />
  23.
                    </td>
  24.
                    <td>
  25.
                        <asp:Label runat="server" ID="Label2"
  26.
                           text='<%# Eval("Email") %>' />
  27.
                    </td>
  28.

  29.
                </tr>
  30.
                </ItemTemplate>
  31.

  32.
                <FooterTemplate>
  33.
                    </table>
  34.
                </FooterTemplate>
  35.

  36.
              </asp:Repeater>
  37.
              <asp:Button ID="prevButton" runat="server"
onclick="prevButton_Click"
  38.
             Text="Previous" />
  39.
          <asp:Button ID="nextButton" runat="server"
onclick="nextButton_Click"
  40.
             Text="Next" />
  41.
          <br />
  42.
          <br />
  43.
          <asp:TextBox ID="myTextBox" runat="server"
TextMode="MultiLine"></asp:TextBox>
  44.
              <asp:Button ID="myButton" runat="server"
onclick="myButton_Click"
  45.
             Text="Send All" />
  46.
              </ContentTemplate>
  47.
              </asp:UpdatePanel>


Timer's callback function code:

protected void UpdateTimer_Tick(object sender, EventArgs e)
    {
        for (int i = 0; i < _sendIndexBuffer.Count; ++i)
        {
            RepeaterItem ri = myRepeater.Items[_sendIndexBuffer[i]];
            HtmlTableRow tr = ri.FindControl("tr") as HtmlTableRow;

            if (tr != null)
               /tr.Style.Add(HtmlTextWriterStyle.BackgroundColor,
"green");


        _sendIndexBuffer.Clear();

        // myTextBox.Text = DateTime.Now.ToString();
    }