RequiredFieldValidator.AddAttributesToRender Method (HtmlTextWriter)


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Adds the HTML attributes and styles that need to be rendered for the control to the specified HtmlTextWriter object.

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

protected override void AddAttributesToRender(
	HtmlTextWriter writer


Type: System.Web.UI.HtmlTextWriter

A HtmlTextWriter that represents the output stream to render HTML content on the client.

The following code example demonstrates how to override the AddAttributesToRender method in a custom server control so that the RequiredFieldValidator error message always displays as bold.

System_CAPS_security Security 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="" >
    <title>Custom RequiredFieldValidator - AddAttributesToRender - C# Example</title>
    <script runat="server">
      void Button1_Click(Object sender, EventArgs e) 
        if (Page.IsValid) 
          Label1.Text = "Required field is filled!";
          Label1.Text = "Required field is empty!";
    <form id="Form1" method="post" runat="server">
      <h3>Custom RequiredFieldValidator - AddAttributesToRender - C# Example</h3>

      <table border="0" cellpadding="4" cellspacing="0">
        <tr valign="top">
          <td colspan="3">
            <asp:Label ID="Label1" runat="server" Text="Fill in the required field below" />
          <td align="right">Card Number:</td>
            <asp:TextBox id="TextBox1" runat="server" />
              ErrorMessage="Required" />
            <asp:Button id="Button1" runat="server" Text="Validate" OnClick="Button1_Click" />

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

namespace Samples.AspNet.CS.Controls
  [AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
  public sealed class CustomRequiredFieldValidatorAddAttributesToRender : System.Web.UI.WebControls.RequiredFieldValidator
    protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
      // Show the RequiredFieldValidator's error message as bold.
      writer.AddStyleAttribute(System.Web.UI.HtmlTextWriterStyle.FontWeight, "bold");

      // Call the Base's AddAttributesToRender method.

.NET Framework
Available since 1.1
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