Access denied when uploading files to folder using asp.net mvc 3?

I'm currently studying asp.net mvc 3, and right now I'm trying to implement a application where a user can upload a file to a folder:

Here's the first implementation that I have and it's actually working fine, here is the controller code:

   public class FileUploadController : Controller
    {
        //
        // GET: /FileUpload/

        public ActionResult Index()
        {
            return View();
        }
        [HttpPost]
        [ActionName("Upload")]
        public ActionResult Index(FormCollection form)
        {

            string upFolder = Server.MapPath("~/FileUploadFiles/");

            if(!Directory.Exists(upFolder))
            {
                Directory.CreateDirectory(upFolder);
            }
            HttpPostedFileBase photo = Request.Files["fileupload"];

            if (photo != null)
            {
                photo.SaveAs(upFolder+photo.FileName);
                return RedirectToAction("Index");
            }



            return View();
        }

    }

Here is another implementation that I have, I'm getting an error "Access to the path 'UserUploads\Uploads\' is denied." Here is the utitility class that handles the upload:

 public static class FileUploader
    {
        public static char DirSeparator = Path.DirectorySeparatorChar;
        public static string FilesPath = "UserUploads" + DirSeparator + "Uploads" + DirSeparator;

        public static string UploadFile(HttpPostedFileBase file)
        {
            //check if we have a file
            if(file == null)
            {
                return "";
            }

            //make sure the file has content
            if(!(file.ContentLength > 0 ))
            {
                return "";
            }

            string fileName = file.FileName;
            string fileExt = Path.GetExtension(file.FileName);

            //make sure we are able to determine a proper extension
            if(fileExt == null)
            {
                return "";
            }

            //check if directory does not exists
            if(!Directory.Exists(FilesPath))
            {
                Directory.CreateDirectory(FilesPath);
            }

            //set our full path for saving
            string path = FilesPath + DirSeparator + fileName;
            //Save the file
            file.SaveAs(Path.GetFullPath(path));

            //Return the filename
            return fileName;

        }

        public static void DeleteFile(string fileName)
        {
            //Don't do anything if there is no name
            if(fileName.Length > 0)
            {
                return;
            }

            //Set our full path for deleting
            string path = FilesPath + DirSeparator + fileName;

            //Check if our file exists
            if(File.Exists(Path.GetFullPath(path)))
            {
                File.Delete(Path.GetFullPath(path));
            }
        }

Here is the code for the controller:

using MvcFileUpload.Utility;

namespace MvcFileUpload.Controllers
{
    public class UploadFilesController : Controller
    {
        //
        // GET: /UploadFiles/

        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        [ActionName("Upload")]
        public ActionResult Index(HttpPostedFileBase file)
        {

            FileUploader.UploadFile(file);
            return RedirectToAction("Index");
        }

    }
}