c# – Calling JavaScript Function From CodeBehind

The Question :

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Can someone provide good examples of calling a JavaScript function From CodeBehind and Vice-versa?

The Question Comments :

The Answer 1

208 people think this answer is useful

You may try this :


The Answer 2

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C# to JavaScript: you can register script block to run on page like following:

ClientScript.RegisterStartupScript(GetType(),"hwa","alert('Hello World');",true);

replace alert() part with your function name.

For calling C# method from JavaScript you can use ScriptManager or jQuery. I personally use jQuery. You need to decorate the method that you want to call from JavaScript with WebMethod attribute. For more information regarding calling C# method (called PageMethod) from jQuery you can refer to Dave Ward’s post.

The Answer 3

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Calling a JavaScript function from code behind

Step 1 Add your Javascript code

<script type="text/javascript" language="javascript">
    function Func() {

Step 2 Add 1 Script Manager in your webForm and Add 1 button too

Step 3 Add this code in your button click event

ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "text", "Func()", true);

The Answer 4

15 people think this answer is useful

If you need to send a value as a parameter.

string jsFunc = "myFunc(" + MyBackValue + ")";
ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "myJsFn", jsFunc, true);

The Answer 5

15 people think this answer is useful

You can not do this directly. In standard WebForms JavaScript is interpreted by browser and C# by server. What you can do to call a method from server using JavaScript is.

Like this:

Step 1

public partial class Products : System.Web.UI.Page 
    public static List<Product> GetProducts(int cateogryID) 
        // Put your logic here to get the Product list 

Step 2: Adding a ScriptManager on the Page

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true" />

Step 3: Calling the method using JavaScript

function GetProductsByCategoryID(categoryID)
    PageMethods.GetProducts(categoryID, OnGetProductsComplete);

Take a look at this link.

To call a JavaScript function from server you can use RegisterStartupScript:


The Answer 6

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Another thing you could do is to create a session variable that gets set in the code behind and then check the state of that variable and then run your javascript. The good thing is this will allow you to run your script right where you want to instead of having to figure out if you want it to run in the DOM or globally.

Something like this: Code behind:

Session["newuser"] = "false" 

In javascript

var newuser = '<%=Session["newuser"]%>';
 if (newuser == "yes")

The Answer 7

7 people think this answer is useful

You cannot. Codebehind is running on the server while JavaScript is running on the client.

However, you can add <script type="text/javascript">someFunction();</script> to your output and thus cause the JS function to be called when the browser is parsing your markup.

The Answer 8

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You can use literal:

this.Controls.Add(new LiteralControl("<script type='text/javascript'>myFunction();</script>"));

The Answer 9

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Try This in Code Behind and it will worked 100%

Write this line of code in you Code Behind file

string script = "window.onload = function() { YourJavaScriptFunctionName(); };";
ClientScript.RegisterStartupScript(this.GetType(), "YourJavaScriptFunctionName", script, true);

And this is the web form page

<script type="text/javascript">
    function YourJavaScriptFunctionName() {

The Answer 10

5 people think this answer is useful

IIRC Code Behind is compiled serverside and javascript is interpreted client side. This means there is no direct link between the two.

What you can do on the other hand is have the client and server communicate through a nifty tool called AJAX. http://en.wikipedia.org/wiki/Asynchronous_JavaScript_and_XML

The Answer 11

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Working Example :_

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage2.Master" AutoEventWireup="true" CodeBehind="History.aspx.cs" Inherits="NAMESPACE_Web.History1" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
    <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajax" %>

 <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script> 

        <script type="text/javascript">

            function helloFromCodeBehind() {



<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">

 <div id="container"  ></div>


Code Behind

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace NAMESPACE_Web
    public partial class History1 : System.Web.UI.Page
        protected void Page_Load(object sender, EventArgs e)

            ScriptManager.RegisterStartupScript(this, GetType(), "displayalertmessage", "helloFromCodeBehind()", true);


Possible pitfalls:-

  1. Code and HTML might not be in same namespace
  2. CodeBehind="History.aspx.cs" is pointing to wrong page
  3. JS function is having some error

The Answer 12

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ScriptManager.RegisterStartupScript(this, this.Page.GetType(),"updatePanel1Script", "javascript:ConfirmExecute()",true/>

The Answer 13

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I’ve been noticing a lot of the answers here are using ScriptManager.RegisterStartupScript and if you are going to do that, that isn’t the right way to do it. The right way is to use ScriptManager.RegisterScriptBlock([my list of args here]). The reason being is you should only be using RegisterStartupScript when your page loads (hence the name RegisterStartupScript).


ScriptManager.RegisterClientScriptBlock(Page, GetType(String), "myScriptName" + key, $"myFunctionName({someJavascriptObject})", True)

in C#:

ScriptManager.RegisterClientScriptBlock(Page, typeof(string), "myScriptName" + key, $"myFunctionName({someJavascriptObject})", true);

Of course, I hope it goes without saying that you need to replace key with your key identifier and should probably move all of this into a sub/function/method and pass in key and someJavascriptObject (if your javascript method requires that your arg is a javascript object).

MSDN docs:


The Answer 14

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ScriptManager.RegisterStartupScript(Page, GetType(), "JavaFunction", "AlertError();", true);

using your function is enough

The Answer 15

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This is how I’ve done it.

HTML markup showing a label and button control is as follows.

  <form id="form1" runat="server"> 
    <asp:Label ID="lblJavaScript" runat="server" Text=""></asp:Label> 
    <asp:Button ID="btnShowDialogue" runat="server" Text="Show Dialogue" /> 

JavaScript function is here.

<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."); 

Code behind to trigger the JavaScript function is here.

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

The Answer 16

1 people think this answer is useful

this works for me

object Json_Object=maintainerService.Convert_To_JSON(Jobitem);
ScriptManager.RegisterClientScriptBlock(this,GetType(), "Javascript", "SelectedJobsMaintainer("+Json_Object+"); ",true);

The Answer 17

1 people think this answer is useful

Since I couldn’t find a solution that was code behind, which includes trying the ClientScript and ScriptManager like mutanic and Orlando Herrera said in this question (they both somehow failed), I’ll offer a front-end solution that utilizes button clicks to others if they’re in the same position as me. This worked for me:

HTML Markup:

<asp:button ID="myButton" runat="server" Text="Submit" OnClientClick="return myFunction();"></asp:button>


function myFunction() {
    // Your JavaScript code
    return false;

I am simply using an ASP.NET button which utilizes the OnClientClick property, which fires client-side scripting functions, that being JavaScript. The key things to note here are the uses of the return keyword in the function call and in the function itself. I’ve read docs that don’t use return but still get the button click to work – somehow it didn’t work for me. The return false; statement in the function specifies a postback should NOT happen. You could also use that statement in the OnClientClick property: OnClientClick="myFunction() return false;"

The Answer 18

0 people think this answer is useful

I used ScriptManager in Code Behind and it worked fine.

ScriptManager.RegisterStartupScript(UpdatePanel1, UpdatePanel1.GetType(), "CallMyFunction", "confirm()", true);

If you are using UpdatePanel in ASP Frontend. Then, enter UpdatePanel name and ‘function name’ defined with script tags.

The Answer 19

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Thank “Liko”, just add a comment to his answer.

string jsFunc = "myFunc(" + MyBackValue + ")";
ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "myJsFn", jsFunc, true);

Added single quotes (') to variable, otherwise it will give error message:

string jsFunc = "myFunc('" + MyBackValue + "')";

The Answer 20

-1 people think this answer is useful

You can’t call a Javascript function from the CodeBehind, because the CodeBehind file contains the code that executes server side on the web server. Javascript code executes in the web browser on the client side.

The Answer 21

-1 people think this answer is useful

You can expose C# methods on codebehind pages to be callable via JavaScript by using the ScriptMethod attribute.

You cannot call JavaScript from a CodeBehind – that code exists solely on the client.

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