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CssStyleCollection.Add Method (String, String)

Adds a style item to the CssStyleCollection of a control using the specified name/value pair.

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

public void Add(
	string key,
	string value


Type: System.String
The name of the new style attribute to add to the collection.
Type: System.String
The value of the style attribute to add to the collection.


key is null.

If the style item to add exists in the HtmlTextWriterStyle enumeration, use the overload of the Add method that takes an HtmlTextWriterStyle parameter because it is strongly typed. This means that items that are added will be included when viewing items with the get accessor of the Item property.

The following code example demonstrates how to use both overloads of the Add method to add a cascading style sheet to an HtmlSelect, HtmlInputSubmit, and a Label control programmatically.

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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<script runat="server">

  protected void SubmitBtn_Click(object sender, EventArgs e)
    SubmitBtn.Style.Add("letter-spacing", "10px");
    FirstSelect.Style.Add(HtmlTextWriterStyle.Color, FirstSelect.Items[FirstSelect.SelectedIndex].Value.ToString());
    Message.Style.Add(HtmlTextWriterStyle.Color, FirstSelect.Items[FirstSelect.SelectedIndex].Value.ToString());
    Message.Text = "The select style is: " + FirstSelect.Style.Value;

<html xmlns="" >
<head runat="server">
    <title>CssStyleCollection Add</title>
    <form id="form1" runat="server">
    Select a color and then click submit.
    <br />
    <select id="FirstSelect" 
            style="font: 10pt verdana;color:black;" 
        <option value="black">black</option>
        <option value="red">red</option>
        <option value="blue">blue</option>
        <option value="green">green</option>
    <input id="SubmitBtn" 
           runat="server" /><br/>
    <br />
    <asp:Label id="Message"

.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.