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TextBox.TagKey Property

This member overrides WebControl.TagKey, and more complete documentation might be available in that topic.

Gets the HTML tag for the text box control. This property is protected.

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

protected override HtmlTextWriterTag TagKey { get; }

Property Value

Type: System.Web.UI.HtmlTextWriterTag
HtmlTextWriterTag.Textarea if the text box is multiline; otherwise, Input.

The following code example demonstrates how to use the TagKey property to create a custom text box.

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"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom TextBox - TagKey - C# Example</title>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom TextBox - TagKey - C# Example</h3>

            <aspSample:CustomTextBoxTagKey 
              id="TextBox1" 
              runat="server">Hello World!
            </aspSample:CustomTextBoxTagKey>

        </form>
    </body>
</html>
using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
  [AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
  public sealed class CustomTextBoxTagKey : System.Web.UI.WebControls.TextBox
  {
    protected override System.Web.UI.HtmlTextWriterTag TagKey
    {
      get 
      {
        // If the TextMode is MultiLine, return a Textarea tag,  
        // else return an Input tag. 
        if (this.TextMode == System.Web.UI.WebControls.TextBoxMode.MultiLine)
        {
          return System.Web.UI.HtmlTextWriterTag.Textarea;
        }
        else
        {
          return System.Web.UI.HtmlTextWriterTag.Input;
        }
      }
    }
  }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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