MVC4 - Ajax.ActionLink() GET returning 500 internal server error

Question

I'm getting a 500 internal server error when I click on an Ajax.ActionLink. I have a profile page that's made up of a number of partials. Each partial makes Ajax calls to the server to allow for editing of user information related to that specific partial.

I've implemented 3 partials with said functionality that work fine. The one I'm working on now should initially show a list of uploaded images - if the user hasn't uploaded any images the Ajax.ActionLink mentioned previously will be shown, which when clicked will bring the user to a partial that facilitates image uploading.

Here's what I'm seeing in Chrome when I hit the link:

Here's the GET and POST ActionResults:

    //
    // GET: /Tenants/TenantUploadReference

    [HttpGet]
    public ActionResult TenantUploadReference()
    {
        try
        {
            var currentTenant = tenantRepository.GetLoggedInTenant();
            if (currentTenant.ReferencePhotos == null)
            {
                currentTenant.ReferencePhotos = currentTenant.ReferencePhotos ?? new List<ReferencePhoto>();
            }
            return PartialView("_TenantUploadReferencePartial", currentTenant.ReferencePhotos.ToList());
        }
        catch (Exception e)
        {
            ModelState.AddModelError("", e);
            return View();
        }
    }

    //
    // POST: /Tenants/TenantUploadReference

    [HttpPost]
    public ActionResult TenantUploadReference(HttpPostedFileBase file, Tenant tenant)
    {
        try
        {
            if (file != null)
            {
                if (file.ContentLength > 10240)
                {
                    ModelState.AddModelError("file", "The size of the file should not exceed 10 KB");
                    return View();
                }

                var supportedTypes = new[] { "jpg", "jpeg", "png", "JPG", "JPEG", "PNG" };
                var fileExt = System.IO.Path.GetExtension(file.FileName).Substring(1);

                if (!supportedTypes.Contains(fileExt))
                {
                    ModelState.AddModelError("photo", "Invalid type. Only the following types (jpg, jpeg, png) are supported.");
                    return View();
                }

                using (var db = new LetLordContext())
                {
                    var reference = db.Image.Create<ReferencePhoto>();

                    // Convert HttpPostedFileBase to byte array
                    MemoryStream target = new MemoryStream();
                    file.InputStream.CopyTo(target);
                    byte[] photo = target.ToArray();

                    reference.File = photo;
                    reference.Format = fileExt;
                    reference.DateUploaded = DateTime.Now.Date;
                    reference.Description = "";
                    reference.Name = "";

                    db.Image.Add(reference);
                    db.SaveChanges();

                    return PartialView("_TenantReferencePhotosPartial", file);
                }

            }
            else
            {
                return View();
            }
        }
        catch (Exception e)
        {
            ModelState.AddModelError("", e);
            return View();
        }
    }

When I step through the debugger with a break point on the GET ActionResult it hits return PartialView and no exceptions are thrown.

In _TenantUploadReferencePartial I use

@using (Ajax.BeginForm("TenantUploadReference", "Tenants", FormMethod.Post, new AjaxOptions { InsertionMode = InsertionMode.Replace, HttpMethod = "POST", UpdateTargetId = "tenant-reference-photos" }))

and in _TenantReferencePhotosPartial (where the ActionLink throws 500 error) I use this

@if (Model.ReferencePhotos == null)
{
    <h3>You haven't uploaded any references! 
        @Ajax.ActionLink("Upload now?",
            "TenantUploadReference",
            new AjaxOptions
            {
                UpdateTargetId = "tenant-reference-photos",
                InsertionMode = InsertionMode.Replace,
                HttpMethod = "GET",
                LoadingElementId = "ajax-loader"
            })</h3>

It may also be useful to know that other partials on the page work as expected, so I don't think it's an issue with missing scripts. I'm at a loss as to why this is happening - a solution would be much appreciated.

Answer 1

I've solved the problem. I was returning currentTenant.ReferencePhotos.ToList() which threw a ArgumentNullException. Now I'm returning just currentTenant, and the GET is working as expected.