I've following code for file download:

        FileInfo fileInfo = new FileInfo(filePath);

        context.Response.Clear();
        context.Response.ContentType = "application/octet-stream";
        context.Response.AddHeader("Content-Disposition", "attachment; filename=" + System.IO.Path.GetFileName(filePath));
        context.Response.AddHeader("Content-Length", fileInfo.Length.ToString());
        context.Response.WriteFile(filePath);
        context.Response.End();

When I run it on my local IIS6 it works fine. Web browser (tested on IE8, Firefox 3.5.2, Opera 10) shows file length before I start download the file.

When I run this code on remote IIS7, web browser doesn't shows file length. File length is unknown.

Why I don't get file length when this code runs under IIS7?