C#•3y ago

✅ asp.net handling image uploads.

error: NullReferenceException: Object reference not set to an instance of an object.
controller:

 [HttpPost]
        public async Task<IActionResult> Edit(int Id, ClubViewModel _CVM)
        {
            if (!ModelState.IsValid)
            {
                ModelState.AddModelError("", "Failed to edit this club");

                return View("Edit", _CVM);
            }

            var clubUploadingImage = await _clubRepository.GetByIdAsync(Id);

            if (clubUploadingImage == null) return View("Error");

 [HttpPost]
        public async Task<IActionResult> Edit(int Id, ClubViewModel _CVM)
        {
            if (!ModelState.IsValid)
            {
                ModelState.AddModelError("", "Failed to edit this club");

                return View("Edit", _CVM);
            }

            var clubUploadingImage = await _clubRepository.GetByIdAsync(Id);

            if (clubUploadingImage == null) return View("Error");

here is the error

            var photoResult = await _photoService.AddPhotoAsync(_CVM.Image);

            var photoResult = await _photoService.AddPhotoAsync(_CVM.Image);

here is after the error

            if (photoResult.Error != null)
            {
                ModelState.AddModelError("Image", "Unable to upload photo");
                return View(_CVM);
            }

            if (clubUploadingImage.Image == null)
            {
                _ = await _photoService.DeletePhotoAsync(clubUploadingImage.Image);
            }

            var updateClubImage = new Club()
            {
                Id = _CVM.Id,
                Title = _CVM.Title,
                Description = _CVM.Description,
                Image = photoResult.Url.ToString(),
                AddressId = _CVM.AddressId,
                Address = _CVM.Address,
                ClubCategory = _CVM.ClubCategory,
            };

            _clubRepository.Update(updateClubImage);

            return RedirectToAction("Index");
        }

            if (photoResult.Error != null)
            {
                ModelState.AddModelError("Image", "Unable to upload photo");
                return View(_CVM);
            }

            if (clubUploadingImage.Image == null)
            {
                _ = await _photoService.DeletePhotoAsync(clubUploadingImage.Image);
            }

            var updateClubImage = new Club()
            {
                Id = _CVM.Id,
                Title = _CVM.Title,
                Description = _CVM.Description,
                Image = photoResult.Url.ToString(),
                AddressId = _CVM.AddressId,
                Address = _CVM.Address,
                ClubCategory = _CVM.ClubCategory,
            };

            _clubRepository.Update(updateClubImage);

            return RedirectToAction("Index");
        }

here is the viewModel's image properties

public class ClubViewModel
    {
        public int Id { get; set; } // [Key] not required if the id is declared like this
        public string? Title { get; set; }
        public string? Description { get; set; }
        public IFormFile Image { get; set; }
 public string? ImageURL { get; set; }

public class ClubViewModel
    {
        public int Id { get; set; } // [Key] not required if the id is declared like this
        public string? Title { get; set; }
        public string? Description { get; set; }
        public IFormFile Image { get; set; }
 public string? ImageURL { get; set; }

the actual model

        public string? Image { get; set; }

        public string? Image { get; set; }

PelicandevelopsOP•5/6/23, 6:36 AM

here is the function being called

PelicandevelopsOP•5/6/23, 6:40 AM

System.NullReferenceException: 'Object reference not set to an instance of an object.'

PelicandevelopsOP•5/6/23, 7:12 AM

PelicandevelopsOP•5/6/23, 7:13 AM

it looks like _photoService is null

cap5lut•5/6/23, 7:19 AM

yeah it can only be the being null, do u register the service correctly?

Ccap5lut yeah it can only be the `_photoService` being null, do u register the service co...

PelicandevelopsOP•5/6/23, 7:26 AM

PelicandevelopsOP•5/6/23, 7:26 AM

this is something im new to.

cap5lut•5/6/23, 7:33 AM

u also need to register the service:

(https://learn.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-7.0)
also u can use $code to provide code itself

Dependency injection in ASP.NET Core

Learn how ASP.NET Core implements dependency injection and how to use it.

Ccap5lut u also need to register the service: ```csharp using DependencyInjectionSample.I...

MODiX•5/6/23, 7:33 AM

To post C# code type the following:
```cs
// code here
```

Get an example by typing in chat

If your code is too long, post it to: https://paste.mod.gg/

PelicandevelopsOP•5/6/23, 7:34 AM

aha!

PelicandevelopsOP•5/6/23, 7:34 AM

tyvm let me add that in.

cap5lut•5/6/23, 7:34 AM

also, has the controller an appropriate constructor for the services?

PelicandevelopsOP•5/6/23, 7:35 AM

i only have this. should i add it inside the controller constructor?

cap5lut•5/6/23, 7:36 AM

that would only inject the dependency, u also need to add the photo service as parameter and assign it

PelicandevelopsOP•5/6/23, 7:37 AM

is this new to .7? i wonder why the tut that I'm watching didn't do this

PelicandevelopsOP•5/6/23, 7:37 AM

tyvm

cap5lut•5/6/23, 7:37 AM

that missing parameter is also the reason why it didnt complain at instantiation of the controller that its missing a required dependency

PelicandevelopsOP•5/6/23, 7:38 AM

i may have missed it by mistake. ive been learning for three years now and switched to asp.net. i wish i started here first

cap5lut•5/6/23, 7:38 AM

there are two ways for dependency injection, via constructor or via properties. tho i only have experience with the constructor variant. (feels also cleaner to me than the properties variant)

PelicandevelopsOP•5/6/23, 7:38 AM

properties as in this?

cap5lut•5/6/23, 7:39 AM

these are fields not properties. but that + the shown constructor should work, if u have registered the service as mentioned earlier

PelicandevelopsOP•5/6/23, 7:40 AM

oooohhhhh i got a different error! we're in business.

Ccap5lut these are *fields* not properties. but that + the shown constructor should work,...

PelicandevelopsOP•5/6/23, 7:40 AM

thats a topic i've yet to discover

cap5lut•5/6/23, 7:41 AM

note that there are 3 different methods on how u can register a service
-> one instance for all which require the
-> everthing gets its own instance
-> one instance per scope (asp creates a scope for each incoming request)

cap5lut•5/6/23, 7:45 AM

with properties u can add functionality to accessing the data:

cap5lut•5/6/23, 7:46 AM

of course there is a lot more to properties, but explaining that all here would take too long ;p