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onChange event errors out with undefined function

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User-390139731 posted

Hi all!

I'm just learning ASP.net with visual studio. I think this will be an obvious question but I can't see the forest from the trees yet.
I have a test page called test.aspx - It contains this html:

<asp:Textbox id="myTextbox" runat="server" onChange="txtChanged" AutoPostBack="true"/>

on the test.aspx.cs script I have this snippet:

namespace WebApp { public partial class test: System.Web.UI.Page { public void txtChanged (Object sender, EventArgs e){ Debug.WriteLine("Item changed"); } protected void Page_Load(object sender, EventArgs e) { } }

When running the site, there will be an error saying 'txtChanged' is undefined. I think I'm adding my method either to the wrong file, placing it at the wrong level, or need to add another hook somewhere.

What am I doing wrong?
Wednesday, August 1, 2018 10:41 PM

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User409696431 posted

Please don't post the same question twice. You (and others) will miss the answers. I've answered you in your other post: https://forums.asp.net/t/2144837.aspx?onChange+event+s+designated+function+is+undefined+

Thursday, August 2, 2018 4:03 AM

User283571144 posted

Hi Quick_Question_:

According to your codes, I found you use onChange attribute.

But the asp textbox control doesn't contain the onChange attribute, it only contains the OnTextChanged event.

I suggest you could use OnTextChanged event instead of onchange.

More details, you could refer to below test demo codes:

Notice: This event will be fried when losing focus on the textbox.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="TextBoxChangedEventTest.aspx.cs" Inherits="AspNetNormalIssue.Webform.TextBoxChangedEventTest" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Textbox id="myTextbox" runat="server"   OnTextChanged="txtChanged"   AutoPostBack="true"/>
        </div>
    </form>
</body>
</html>

Code-behind:

using System;
using System.Diagnostics;

namespace AspNetNormalIssue.Webform
{
    public partial class TextBoxChangedEventTest : System.Web.UI.Page
    {
        public void txtChanged(Object sender, EventArgs e)
        {
         
            Debug.WriteLine("Item changed");
            Response.Write("Item changed");
        }

        protected void Page_Load(object sender, EventArgs e)
        {

        }

       
    }
}

Result:

Best Regards,

Brando

Thursday, August 2, 2018 6:33 AM

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onChange event errors out with undefined function

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