How to call javascript function from code-behind

Question

I wrote a javascript with a asp.net page.

In Asp.net Page

<HTML> <HEAD>
     <script type="text/javascript">
      function Myfunction(){
          document.getElementId('MyText').value="hi";
      }
      </script>
</HEAD> <BODY>
<input type="text" id="MyText" runat="server" /> </BODY>

In Code-behind

 Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
  Handles Me.Load
       If Session("My")= "Hi" Then
          I want to call "Myfunction" javascript function
       End If 
 End Sub

How can I do?

possible duplicate of [How to call javascript function from code-behind](http://stackoverflow.com/questions/4847819/how-to-call-javascript-function-from-code-behind) — outis, Jan 31 '11 at 08:02
do you really want to call the function from the code-behind, or do you want function to run when the page load? I think it is the last alternative you want. — Tomas Jansson, Jan 31 '11 at 08:07

Jacob · Answer 1 · 2012-10-12T15:54:54.723

80

One way of doing it is to use the ClientScriptManager:

Page.ClientScript.RegisterStartupScript(
    GetType(), 
    "MyKey", 
    "Myfunction();", 
    true);

edited Oct 12 '12 at 15:54

answered Jan 31 '11 at 08:01

Jacob

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2

Seem like the best way is yours, but what does "MyKey" is ? – Antoine Pelletier Sep 09 '15 at 20:31
5

The key is just a unique identifier to help avoid emitting the same script twice. It can be anything. – Jacob Sep 10 '15 at 15:36
the best solution, very simple – Gabriel Bernardone May 11 '18 at 13:41
2

the key shall be a GUID! – Pranesh Janarthanan Oct 23 '19 at 13:30
See here if you want the javascript function to execute after the page has loaded https://stackoverflow.com/a/40335689/74585 – Matthew Lock Aug 25 '20 at 08:05

score 44 · Accepted Answer · edited Nov 06 '20 at 22:35

This is a way to invoke one or more JavaScript methods from the code behind. By using Script Manager we can call the methods in sequence. Consider the below code for example.

ScriptManager.RegisterStartupScript(this, typeof(Page), "UpdateMsg", 
    "$(document).ready(function(){EnableControls();
    alert('Overrides successfully Updated.');
    DisableControls();});", 
true);

In this first method EnableControls() is invoked. Next the alert will be displayed. Next the DisableControls() method will be invoked.

score 14 · Answer 3 · edited Feb 24 '17 at 05:18

14

There is a very simple way in which you can do this. It involves injecting a javascript code to a label control from code behind. here is sample code:

<head runat="server"> 
    <title>Calling javascript function from code behind example</title> 
        <script type="text/javascript"> 
            function showDialogue() { 
                alert("this dialogue has been invoked through codebehind."); 
            } 
        </script> 
</head>

..........

lblJavaScript.Text = "<script type='text/javascript'>showDialogue();</script>";

Check out the full code here: ~~http://softmate-technologies.com/javascript-from-CodeBehind.htm~~ (dead)
Link from Internet Archive: https://web.archive.org/web/20120608053720/http://softmate-technologies.com/javascript-from-CodeBehind.htm

edited Feb 24 '17 at 05:18

spacer

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answered Jun 02 '12 at 07:49

evaaggy

187
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4

2

Unfortunately the link is broken :-( – Hugo Nava Kopp Dec 14 '15 at 00:23
Loving this solution - it almost feels like cheating. I suspect it may not be suitable for every scenario but I'm hard pressed to think of a case where it wouldn't work. – cymorg May 17 '16 at 23:49

score 1 · Answer 4 · answered Apr 16 '19 at 15:31

If the order of the execution is not important and you need both some javascript AND some codebehind to be fired on an asp element, heres what you can do.

What you can take away from my example: I have a div covering the ASP control that I want both javascript and codebehind to be ran from. The div's onClick method AND the calendar's OnSelectionChanged event both get fired this way.

In this example, i am using an ASP Calendar control, and im controlling it from both javascript and codebehind:

Front end code:

        <div onclick="showHideModal();">
            <asp:Calendar 
                OnSelectionChanged="DatepickerDateChange" ID="DatepickerCalendar" runat="server" 
                BorderWidth="1px" DayNameFormat="Shortest" Font-Names="Verdana" 
                Font-Size="8pt" ShowGridLines="true" BackColor="#B8C9E1" BorderColor="#003E51" Width="100%"> 
                <OtherMonthDayStyle ForeColor="#6C5D34"> </OtherMonthDayStyle> 
                <DayHeaderStyle  ForeColor="black" BackColor="#D19000"> </DayHeaderStyle>
                <TitleStyle BackColor="#B8C9E1" ForeColor="Black"> </TitleStyle> 
                <DayStyle BackColor="White"> </DayStyle> 
                <SelectedDayStyle BackColor="#003E51" Font-Bold="True"> </SelectedDayStyle> 
            </asp:Calendar>
        </div>

Codebehind:

        protected void DatepickerDateChange(object sender, EventArgs e)
        {
            if (toFromPicked.Value == "MainContent_fromDate")
            {
                fromDate.Text = DatepickerCalendar.SelectedDate.ToShortDateString();
            }
            else
            {
                toDate.Text = DatepickerCalendar.SelectedDate.ToShortDateString();
            }
        }

score 0 · Answer 5 · answered Apr 06 '21 at 03:23

asp:run javascript method

Add this line to the bottom of the page before </form> tag, at least under the js function you wrote.

the reason of doning this is avoid calling your method before your browse knowing what is the funcion and finally do nothing.

<% Response.Write($"<script>yourfunction('{Config.id}');</script>"); %>

ps: I've tried all methods up there but nothing worked fine for me. And I figure out this easy and wonder way of calling js method on my own!

How to call javascript function from code-behind

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