Messaggio attesa (loadign page)

            Thread t = new  Thread(() => {
              ReportDocument r = new ReportDocument();
                r.Load(...)
              ....
  
            });
            t.Priority = ThreadPriority.Lowest;
            t.Start();

<asp:UpdateProgress ID="upProgress" runat="server">
        <ProgressTemplate>
          <style type="text/css">
    .PRORESS_overlay {
        position: fixed;
        z-index: 98;
        top: 0px;
        left: 0px;
        right: 0px;
        bottom: 0px;
        background-color: #aaa;
        filter: alpha(opacity=80);
        opacity: 0.8;
    }

    .PRORESS_overlayContent {
        /*position: fixed;*/
        z-index: 999;
        margin-left: auto;
        margin-right: auto;
        width: 80px;
        height: 80px;
    }

        .PRORESS_overlayContent img {
            z-index: 999999;
            padding-top: 300px;
        }
</style>


<div class="PRORESS_overlay">
    <div class="PRORESS_overlayContent">
        <img src="/img/loading.gif" alt="Loading..." width="60" />
    </div>
</div>

        </ProgressTemplate>
    </asp:UpdateProgress>