Try this, I am using the jQuery file from Google.
HTML
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="lblDownloadSpeed" runat="server" />
</div>
</form>
</body>
</html>
Namespaces
using System.Net;
Code
protected void Page_Load(object sender, EventArgs e)
{
int jQueryFileSize = 261; //Size of File in KB.
WebClient client = new WebClient();
DateTime startTime = DateTime.Now;
client.DownloadFile("http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.js", Server.MapPath("~/jQuery.js"));
DateTime endTime = DateTime.Now;
lblDownloadSpeed.Text = string.Format("Download Speed: {0}KB/s", Math.Round((jQueryFileSize / (endTime - startTime).TotalSeconds), 0));
}
Screenshot
