Altering CSS at runtime using C#.

Below sample code shows how to alter the CSS at runtime,I have placed the label inside div and added runat
attribute.In page load,I have assigned the CSS name to div.

<div>
        <asp:Button ID = "Button1" runat = "server" OnClick = "Button1_Click" Text = "Button" />
        <div id = "divName" runat = "server">
            <asp:Label ID = "Label1" runat = "server" Text = "Name: "></asp:Label>
        </div>
    </div>

.lblStyle
{
    text-decoration:none;
    font-weight: bold;
    font-size:12px;
    color:#007ddd;
}

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
     divName.Attributes["class"] = "lblStyle";
  }
}