CODEWITHSUNDEEP
javascriptasp.net
Null Pointer
Null Pointer

Reputation: 9289

getElementById is not working in asp.net

In my application i just want to alert the value in the text box using javascript .

aspx page code

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>

    <script type="text/javascript">
        alert("hi");
        alert(document.getElementById('<%=textbox1.ClientID%>').value);
 </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:TextBox  runat="server" ID="textbox1"  Text="asdsad">
            </asp:TextBox>
    </div>
    </form>
</body>
</html>

I only get alert 'hi' ..after that i get an error " object required" . whats the reason?

Upvotes: 1

Views: 6262

Answers (4)

Joseph Le Brech
Joseph Le Brech

Reputation: 6653

The ID you are trying to get is a server side id and not the html id of the element, if you checked using firebug you will notice that the id has loads of extra letters and numbers inserted by asp.net, i'd recommend using jquery instead to walk into the dom to select the specific element.

You could also add a name and getByName.

Upvotes: 1

Rahul.R.Parmar
Rahul.R.Parmar

Reputation: 84

Please change the script location, put the script code on bottom of the page.Just After the complete with form tag.

Upvotes: 1

COBOLdinosaur
COBOLdinosaur

Reputation: 294

The page is not loaded yet. You have to put the code in a function and then trigger with

onload=yourfunction;

Upvotes: 1

ipr101
ipr101

Reputation: 24236

Your code is running before the element has been displayed on the screen. Try - 

window.onload = function() {
     alert("hi");
     alert(document.getElementById('<%=textbox1.ClientID%>').value);
}

Or move your script to the bottom of the page as suggested by Tejs in the comments below.

Upvotes: 4

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