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WebControl.Attributes Property

Gets the collection of arbitrary attributes (for rendering only) that do not correspond to properties on the control.

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

public AttributeCollection Attributes { get; }

Property Value

Type: System.Web.UI.AttributeCollection
A AttributeCollection of name and value pairs.

The Attributes collection contains a collection of all attributes declared in the opening tag of a Web server control. This allows you to programmatically control the attributes associated with a Web server control. You can add attributes to the collection or remove attributes from the collection.


This property is rendered with all attributes in the collection in the control’s opening tag, regardless of the browser settings. Not all browsers support every attribute that is rendered. The unsupported attributes are usually ignored by the browser.


You cannot add client-side script to a WebControl instance using the Attributes collection. To add client-side script, use the ClientScript property on the Page control.

The following example illustrates how the Attributes property of a WebControl can be used to run a JavaScript command when the TextBox control loses focus.


The following code sample uses the single-file code model and may not work correctly if copied directly into a code-behind file. This code sample must be copied into an empty text file that has an .aspx extension. For more information on the Web Forms code model, see ASP.NET Web Page Code Model.

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.

<%@ Page Language="C#" AutoEventWireup="True" %>

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<html xmlns="" >
    <title>Attributes Property of a Web Control</title>
<script language="C#" runat="server">

        void Page_Load(Object sender, EventArgs e) {
           TextBox1.Attributes["onblur"]="javascript:alert('Hello! Focus lost from text box!!');";    

    <h3>Attributes Property of a Web Control</h3>
 <form id="form1" runat="server">

    <asp:TextBox id="TextBox1" columns="54" 
     Text="Click here and then tap out of this text box" 


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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