Generate an image from outstream asp.net 3.5

public static void ProcessDirectory(string targetDirectory)
   {

       // string[] fileEntries = Directory.GetFiles(targetDirectory, "*.jpg");
       var fileEntries = Directory.GetFiles(targetDirectory, "*.jpg");
       //if (photos.Count() == 0)
       //{
       //    Response.Redirect("~/Images/gallery-empty.png");
       //    return;
       //}
       // Process the list of files found in the directory.



       using (var generator = new MultiThumbnailGenerator())
       {
           foreach (var photo in fileEntries)
           {
               using (var imageStream = new System.IO.MemoryStream(photo.FileContents)) //error
               {
                   using (var image = System.Drawing.Image.FromStream(imageStream))
                   {
                       generator.AddImage(image);
                   }
               }
           }
           using (var outStream = new System.IO.MemoryStream())
           {
               generator.WritePngToStream(outStream);
               // var image = new WebImage(outStream);
               //   image.Write();
           }
       }
   }