Question

Here is a controller action method that I have to upload a user’s profile image…

    [HttpPost]
    public ActionResult UploadPhoto(int id, FormCollection form)
    {
        Profile profile = db.Profiles.Find(id);

        var file = Request.Files[0];

        if (file.ContentLength > 512000)
        {
            ModelState.AddModelError(string.Empty, "Please limit your photo to 500 KB");
        }

        bool IsJpeg = file.ContentType == "image/jpeg";
        bool IsPng = file.ContentType == "image/png";
        bool IsGif = file.ContentType == "image/gif";

        if (!IsJpeg && !IsPng && !IsGif)
        {
            ModelState.AddModelError(string.Empty, "Only .jpeg, .gif, and .png images allowed");
        }

        if (file == null || file.ContentLength <= 0)
        {
            ModelState.AddModelError(string.Empty, "You must select an image to upload");
        }

        if (ModelState.IsValid)
        {
            try
            {
                string newFile = Path.GetFileName(file.FileName);
                file.SaveAs(Server.MapPath("/Content/users/" + User.Identity.Name + "/" + newFile));
                profile.ProfilePhotoPath = "/Content/users/" + User.Identity.Name + "/" + newFile;
                UpdateModel(profile);
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
        return View();
    }

When I attempt to upload an image and step through it…

When the application hits this line:

profile.ProfilePhotoPath = "/Content/users/" + User.Identity.Name + "/" + newFile;

It shows the ProfilePhotoPath value to be “System.Web.HttpPostedFileWrapper”

Now when the application hits the next line:

UpdateModel(profile);

It shows the ProfilePhotoPath value to be “/Content/users/WebWired/myprofilepic.png” , as it should…

But then, when the application hits the next line:

db.SaveChanges();

All of a sudden the ProfilePhotoPath value is “System.Web.HttpPostedFileWrapper” again… and that is how it is saved…

If that isn’t odd enough, it did work before I started adding logic to the file upload, but that really shouldn’t have anything to do with it because it passes all of that up…

Does anyone understand what is going on here, why is it doing this, am I doing something wrong?

Answer 1

UpdateModel() updates your profile object with values from the controller’s value provider – i.e., POST parameters etc. If it finds a POST parameter called “ProfilePhotoPath”, your profile.ProfilePhotoPath property will be set to that value, overwriting the value you’ve just set manually.

Your <input type="file"> field (or whatever method you use to post the file to the server) seems to have a name attribute: “ProfilePhotoPath”. That field will be turned into a HttpPostedFileWrapper object on the server, containing the information about the posted file (content length, type, filename etc.). And it’s that object UpdateModel will assign to your profile.ProfilePhotoPath property (because it has the same name as the property). Since it’s assigning an object to a string property, it’ll coerce the object into a string, yielding “System.Web.HttpPostedFileWrapper”.