How to upload multiple files using multiple fileupload controls in asp.net?

I have a webpage(.aspx) which contains MULTIPLE FileUpload controls.

Default.aspx

<asp:FileUpload ID="FileUploadPort" runat="server" CssClass="Upload"  Multiple="Multiple"/>
<asp:FileUpload ID="FileUploadSearchImages" runat="server" CssClass="Upload"  Multiple="Multiple"/>

Default.aspx.cs

protected void btnSubmit_Click(object sender, EventArgs e)
{
       string filenm = string.Empty;
       HttpFileCollection fileCollection = Request.Files;
       for (int i = 0; i < fileCollection.Count; i++)
       {
           HttpPostedFile uploadfile = fileCollection[i];
           if (uploadfile.ContentLength > 0)
            {
              string filename = uploadfile.FileName;
              string imgFolder = ConfigurationManager.AppSettings["AdminSearchImgFolderPath"];
              System.Drawing.Image image = System.Drawing.Image.FromStream(uploadfile.InputStream); 
              image.Save(imgFolder + "\\" + GetSearchImageFileName("TEST"), ImageFormat.Jpeg);

             }
        }
    }

Here, Request.Files will get collectively all files from both the FileUploadControls.

I am NOT able to IDENTIFY which file(s) are from specific FileUpload control?

I know its possible in 4.5 but my current framework is 4.0 and i dont want to upgrade to 4.5. Any solution using existing 4.0 framework??

Help appreciated!

Please note: This is not DUPLICATE question as my requirement is to upload and identify the files of different fileupload controls on single page.