OnTextChanged Method

TextBox.OnTextChanged Method

Raises the TextChanged event. This allows you to handle the event directly.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

protected virtual void OnTextChanged(
	EventArgs e


Type: System.EventArgs

A EventArgs that contains event information.

The TextChanged event is raised when the content of the text box changes between posts to the server.


A TextBox control must persist some values between posts to the server for this event to work correctly. Be sure that view state is enabled for this control.

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The OnTextChanged method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:

When overriding OnTextChanged in a derived class, be sure to call the base class's OnTextChanged method so that registered delegates receive the event.

The following code example demonstrates how to override the OnTextChanged method so that it always marks a custom TextBox server control as having been modified.

Security noteSecurity Note:

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
<html xmlns="http://www.w3.org/1999/xhtml" >
        <title>Custom TextBox - OnTextChanged - C# Example</title>
        <form id="Form1" method="post" runat="server">
            <h3>Custom TextBox - OnTextChanged - C# Example</h3>

              runat="server">Hello World!

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
  [AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
  public sealed class CustomTextBoxOnTextChanged : System.Web.UI.WebControls.TextBox
    private bool isDirty = false;

    protected override void OnTextChanged(System.EventArgs e)
      // Call the base OnTextChanged method. 

      // Change the dirty flag to True.
      isDirty = true;

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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