Show Update Progress During Export

Question

Using the below Java Script to show the loader once the Export To Excel button is clicked.

<script type="text/javascript">
    function showProgress() {
        var updateProgress = $get("<%= UpdateProgress1.ClientID %>");
        updateProgress.style.display = "block";
    }
</script>


<asp:Button ID="btntoExcel" runat="server" Text="Export to Excel"  onclick="btntoExcel_Click" OnClientClick="showProgress()" Width="115px" 
                CssClass="styleShowData" Font-Size="Smaller" />

Everything is working fine but the loader keeps on loading after saving the file in system also.

Don't know how to stop the loader since in JS it is mentioned as

updateProgress.style.display = "block"

Any suggestion will be highly helpful.

Thanks in advance.

Adding Whole Code Below

<%@ Page Language="VB" AutoEventWireup="true" CodeFile="ViewReport.aspx.vb" Inherits="ViewReport" %>

Status Report

    <script type="text/javascript">
        function showProgress() {
            var updateProgress = $get("<%= UpdateProgress1.ClientID %>");
            updateProgress.style.display = "block";
        }

        function hideProgress() {
            var updateProgress = $get("<%= UpdateProgress1.ClientID %>");
            updateProgress.style.display = "none";
        }   
    </script> 

<div runat="server" id="divPopupWindow" align="Left" style="position: relative; top: -11px; left: 0px; background-color: #C8B49B;">
    <marquee behavior="alternate"><asp:Label ID="mqHeader1" runat="server" Text="Scrolling Employee Info"></asp:Label></marquee>

    <br />
        <asp:LoginStatus ID="LoginStatus1" runat="server" />
    <br /><br />

    <asp:UpdatePanel runat="server" ID="UpdatePanel_1">
        <ContentTemplate>

        <div runat="server" id="divMyPageWidth_2" align="Left" style="position: relative; height: 10%; left: 0px; background-color: #C8B49B;">

        <asp:Button ID="btntoExcel" runat="server" Text="Export to Excel"  onclick="btntoExcel_Click" OnClientClick="showProgress()" Width="115px" 
            CssClass="styleShowData" Font-Size="Smaller" />

        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

        <asp:Button ID="btnGotoMainPage" runat="server" Text="Goto Main Page"  
        Width="118px" CssClass="stGotoMainPage" 
        Font-Size="Smaller" />

                <br />
                <table>
                    <tr>
                        <td class="style2">
                            <asp:DropDownList ID="ddlStatusSelection" runat="server">
                                <asp:ListItem Selected="True">Approved</asp:ListItem>
                                <asp:ListItem>Pending</asp:ListItem>
                                <asp:ListItem>Rejected</asp:ListItem>
                            </asp:DropDownList>
                        </td>

                        <td class="style3">
                            <asp:DropDownList ID="ddlShowRecordsCount" runat="server">
                                <asp:ListItem Selected="True">25</asp:ListItem>
                                <asp:ListItem>50</asp:ListItem>
                                <asp:ListItem>100</asp:ListItem>
                                <asp:ListItem>200</asp:ListItem>
                                <asp:ListItem>300</asp:ListItem>
                                <asp:ListItem>400</asp:ListItem>
                                <asp:ListItem>500</asp:ListItem>
                                <asp:ListItem>All</asp:ListItem>
                            </asp:DropDownList>
                        </td>
                        <td>
                            <asp:Button ID="Button1" runat="server" Text="Show Data"  
                            CssClass="styleShowData" />
                        </td>
                    </tr>
            </table>

        <div runat="server" id="divMyPageWidth" align="Left" style="position: relative; background-color: #C8B49B; overflow: scroll">
                <asp:GridView ID="gvScreenToExcel" runat="server" AutoGenerateColumns="false" HeaderStyle-Wrap="True" Height="190px" Width="380px" 
                    BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px" 
                    RowStyle-Wrap="false"  Font-Size="Small" >
                    <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
                    <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
                    <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
                    <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
                    <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
                    <SortedAscendingCellStyle BackColor="#FFF1D4" />
                    <SortedAscendingHeaderStyle BackColor="#B95C30" />
                    <SortedDescendingCellStyle BackColor="#F1E5CE" />
                    <SortedDescendingHeaderStyle BackColor="#93451F" />
                    <AlternatingRowStyle BackColor="#FFE7CE" />
                    <Columns>
                        <asp:BoundField DataField="Rec_Num" HeaderText="Record #" />
                        <asp:BoundField DataField="Remarks" HeaderText="Remarks" />
                    </Columns>
                </asp:GridView>
            </div>

        </div>
        </ContentTemplate>

        <Triggers>
            <asp:PostBackTrigger ControlID = "btntoExcel" />
        </Triggers>

    </asp:UpdatePanel>

    <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel_1">
    <ProgressTemplate>
        <div class="modal">
            <div class="center">
                <img alt="" src="Loader.gif" />
            </div>
            </div>
        </ProgressTemplate>
    </asp:UpdateProgress>
  </div>
</form>

Answer 1

In your code behind inside the btntoExcel_Click event add the following after the export logic is complete.

ScriptManager.RegisterStartupScript(Me, Page.GetType, "Script", "hideProgress();", True)

Answer 2

Some facts about this scenario and provided information before a solution:

• The real downloading should occur during a regular (NOT async) postback. So, registering the "asp:PostBackTrigger" is correct, in general. Otherwise, Sys.WebForms.PageRequestManagerParserErrorException - what it is and how to avoid it.

• NO straightforward way to get notifications in the client-side code and executing any kind of startup scipts (RegisterStartupScript, etc.) from code behind has NO effect, when the HttpReponse.End method (usually/always used during export) is involved.

If there is a strict requirement to show a custom progress indicator (instead of the browsers' one, which is running during downloading), implement the following solution:

• Subscribe to the UpdatePanel's client-side events via the Sys.WebForms.PageRequestManager,
• Execute an async request in order to show the progress indicator. For example, mark the "btntoExcel" button as a asp:AsyncPostBackTrigger instead. The progress indicator should appear,
• Click the "btntoExcel" button to start a routine. Handle the button's SERVER-SIDE Click event and save a created EXCEL file to a memory or to a server folder,
• Handle the client-side UpdatePanel's "endRequest" event. The progress indicator should be already hidden. Initiate a real postback to the server (for example, by adding a hidden "asp:PostBackTrigger" button or use a raw "__doPostBack" function),
• Handle this button's SERVER-SIDE Click event and perform a real download (a previolsy created file).

Below is a complete working code tested with the provided markup:

<script type="text/javascript">
    function showProgress() {
        //var updateProgress = $get("<%= UpdateProgress1.ClientID %>");
        //updateProgress.style.display = "block";
    }
    var prm = Sys.WebForms.PageRequestManager.getInstance();
    prm.add_initializeRequest(prm_InitializeRequest);
    prm.add_endRequest(prm_EndRequest);
    function prm_InitializeRequest(sender, args) {
        alert("Starting Update Panel Async Request... Saving File... Displaying Progress Indicator...");
    }
    function prm_EndRequest(sender, args) {
        alert("Update Panel Async Request Finished. File Saved, But Not Yet Downloaded. Progress Indicator Should Be Already Hidden. Starting Real Download...");
        var btnDoRealDownloadClientObject = $get("<%= btnDoRealDownload.ClientID %>");
        btnDoRealDownloadClientObject.click();
    }
</script>

<asp:UpdatePanel runat="server" ID="UpdatePanel_1">
    <ContentTemplate>
        ...
        <asp:Button ID="btntoExcel" runat="server" Text="Export to Excel" OnClick="btntoExcel_Click" OnClientClick="showProgress()" ... />
        <asp:Button ID="btnDoRealDownload" runat="server" OnClick="btnDoRealDownload_Click" style="display: none" ... />
        ...
    </ContentTemplate>

    <Triggers>
        <%--<asp:PostBackTrigger ControlID="btntoExcel" />--%>
        <asp:AsyncPostBackTrigger ControlID="btntoExcel" />
        <asp:PostBackTrigger ControlID="btnDoRealDownload" />
    </Triggers>

</asp:UpdatePanel>

<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel_1">
    ...
</asp:UpdateProgress>

//CS
protected void btntoExcel_Click(object sender, EventArgs e) {
    Session["SavedFile"] = SAVE_FILE_AS_MEMORY_STREAM;
    ...
}

protected void btnDoRealDownload_Click(object sender, EventArgs e) {
    MemoryStream stream = Session["SavedFile"] as MemoryStream;
    ...
    Page.Response.BinaryWrite(stream.ToArray());
    Page.Response.End();
}


'VB
Protected Sub btntoExcel_Click(ByVal sender As Object, ByVal e As EventArgs)
    Session("SavedFile") = SAVE_FILE_AS_MEMORY_STREAM
    ...
End Sub

Protected Sub btnDoRealDownload_Click(ByVal sender As Object, ByVal e As EventArgs)
    Dim stream As MemoryStream = CType(Session("SavedFile"), MemoryStream)
    ...
    Page.Response.BinaryWrite(stream.ToArray)
    Page.Response.End
End Sub