Step 1: Open Visual Studio 2008/2010 and select -> File -> New -> Website > ASP.NET web site from the dialog and hit Ok.

Step 2: Download uploaded .Zip file from this article. Extract it and copy Scripts folder from extracted folder and paste it in your project.

Step 3 : Add these highlighted lines in the <head> section of your Default.aspx page as shown below:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!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>Uplaoding Multiple Files</title>
 <script type="text/javascript" src="Scripts/jquery-1.4.4.min.js"></script>
 <script type="text/javascript" src="Scripts/swfobject.js"></script>
 <script type="text/javascript" src="Scripts/jquery.uploadify.v2.1.4.min.js"></script>
 <script type="text/javascript">
 $(document).ready(function () {
$('#UploadFiles').uploadify({
'uploader': 'Scripts/uploadify.swf',
'script': 'UploadFiles.aspx',
'cancelImg': 'Scripts/cancel.png',
'auto': 'true',
'multi': 'true',
'buttonText': 'Select Files',
'queueSizeLimit': 500,
'simUploadLimit': 2
});
});
</script>
</head>
<body>
 <form id="form1" runat="server">
 </form>
</body>
</html>

Step 4: Add a line as shown below to the body section in the Default.aspx page.

<body>
 <form id="form1" runat="server">
 <div id="UploadFiles"></div>
 </form>
</body>

Step 5: Create another .aspx page and name it "UploadFiles.aspx". Replace code of your UploadFiles.aspx.cs file with the code given below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;

public partial class UploadFiles : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
HttpPostedFile uploads = Request.Files["FileData"];
string file = System.IO.Path.GetFileName(uploads.FileName);
string Apath = Server.MapPath("~/") + "UploadedFiles";
if (!Directory.Exists(Apath))
Directory.CreateDirectory(Apath);
string AppPath = Server.MapPath("~/");
uploads.SaveAs(Apath + "\\" + file);
}
}

Step 6 : Add this line in web.config file of your project under <system.web> section.

<system.web>

<httpRuntime maxRequestLength="102400"></httpRuntime>

</system.web>

Press F5 and start uploading ……..