her er der et lille eksempel (i dit tilfælde, så skal du skifte background-color ud med background image)
codebind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Default3 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Page_PreRender(object sender, EventArgs e)
{
if (!IsPostBack)
{
Content.Attributes.CssStyle.Add("background-color", "yellow");
}
}
protected void Button1_Click(object sender, EventArgs e)
{
Content.Attributes.CssStyle.Add("background-color", "blue");
}
}
.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>
<!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 runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<div id="Content" runat="server">
<p>Dette er en test</p>
<p>for at vide hvordan man skifter bagrundsfarven ud dynamisk via codebehind</p>
<p>
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
</p>
</div>
</div>
</form>
</body>
</html>