Error while uploading file after deployment

I have uploaded my MVC application on appharbor for testing purpose yesterday.But after deployed,when i try to upload images from my computer it is showing me the following error:

 

[HttpPost]

public ActionResult Upload_Sample_Product(SampleProduct product, HttpPostedFileBase file)

{

try

{

if (ModelState.IsValid)`

{

if (file != null)

{

var extension = Path.GetExtension(file.FileName);

file.SaveAs(HttpContext.Server.MapPath("~/Images/") + file.FileName);

product.Image = file.FileName;

}

db.SampleProducts.Add(product);

db.SaveChanges();

return RedirectToAction("ProductView");

}

}

catch (Exception ex)

{

return Content("" + ex);

}

return View();

}

I have given permission(NETWORK SERVICE) to the folder where the images are stored.But still it is not working.