ASP.NET trigger javascript function from Server side

Posted on 2014-09-04
Last Modified: 2014-09-19
hi Experts,

  On the click of a button , some server side process is happening  .  I already have a small piece of javascript ( runs at on clientclick) to show a  'waiting image'  .
    The javascript line of code is
            document.getElementById("HiddenLoadingImage").style.display = 'block';
    (The defualt display state of the Image is hidden  and it is shows up only when the button is clicked)

 Also, when the server  processing is over, I have a  server side line of code to show a message that the processing is done
    System.Web.HttpContext.Current.Response.Write( _
           "<SCRIPT LANGUAGE='JavaScript'> alert('Process Done')</SCRIPT>")
    But my issue is -  The Waiting image  is still visible when the Alert of  "Process Done"  pops up.  
    How can I  hide the image first and then show the Alert ?


Question by:Sam OZ
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LVL 12

Expert Comment

by:Ramkisan Jagtap
ID: 40303165
Please check the default state of the image. I doubt if it is hidden when it is loaded.

or you can try editing your server side script as below:

 System.Web.HttpContext.Current.Response.Write( _
           "<SCRIPT LANGUAGE='JavaScript'> alert('Process Done');
document.getElementById("HiddenLoadingImage").style.display = 'none';     </SCRIPT>")

Author Comment

by:Sam OZ
ID: 40303574
Hi Ramkisan,

     I am not sure I stated my issue clearly . When the alert pops up the image is visible. But if I click ok, the image becomes invisible

 I already tired the code you suggested . It doesn't work , unfortunately
LVL 12

Expert Comment

by:Ramkisan Jagtap
ID: 40305088
HI Sam,

Just give a try with following:

System.Web.HttpContext.Current.Response.Write( _
            "<SCRIPT type='text/javascript'>  document.getElementById("HiddenLoadingImage").style.display = 'none';
alert('Process Done');
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Author Comment

by:Sam OZ
ID: 40305099
Hi Ram,

   I have tried that too,  That is not the solution.
LVL 12

Expert Comment

by:Ramkisan Jagtap
ID: 40305102
If possible, Can you please post your code here?

Author Comment

by:Sam OZ
ID: 40305139
Hi Ram,

   Please see the attachment for the test code . ( You need to have an image by name Spinner.jpg  under the folder \images  )

 Just a correction  in my code ---  
      Use either    System.Web.HttpContext.Current.Response.Write
            or  ScriptManager.RegisterStartupScript
       ( You need to comment out one of thse)
LVL 12

Expert Comment

by:Ramkisan Jagtap
ID: 40305159
Hello Sam,

Change you code as below:

<html xmlns="">

<head id="Head1" runat="server">
   <script type="text/javascript" language="javascript">

       function AlertClient() {
           document.getElementById("HiddenLoadingImage").style.display = 'none';
           alert("Test Done");

       function DisplayLoadingImage() {
           document.getElementById("HiddenLoadingImage").style.display = "block";



<body onload="AlertClient()">
    <form id="form1" runat="server">
        <img id='HiddenLoadingImage' src="Images/Spinner.jpg" style="display:none"/>
        <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="DisplayLoadingImage()" />

 Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim strMessage As String
        strMessage = "This is test"
    End Sub

    Sub WasteTime()
        Dim i, j, k As Integer
        For i = 0 To 1000
            For j = 0 To 1000
                For k = 0 To 100

    End Sub

Author Comment

by:Sam OZ
ID: 40305278
Hi Ram,

    It can't happen on the Onload in the client . it should happen only after the Button is clicked ( In my actual code there are many other controls)

 Also , Infact, strictly speaking , the Alert should come with the value of a server variable ( But that is not the real problem I face)
LVL 12

Accepted Solution

Ramkisan Jagtap earned 500 total points
ID: 40305400
Are you using ajax in your project? If yes you can make a use of Update Progress from ajaxtoolkit dll

Author Comment

by:Sam OZ
ID: 40311564
Hi Ram & other Experts,

    AJAX is not used in this project , unfortunately  ( This is a revamp project ) . Also I am a little naive with AJAX

    Is there really a way to do this with no AJAX ?

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