C#•2y 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; }

28 Replies

Candyroll93OP•2y ago

here is the function being called

public async Task<ImageUploadResult> AddPhotoAsync(IFormFile uploadedFile)
        {
            var uploadResult = new ImageUploadResult();

            if (uploadedFile.Length > 0)
            {
                using var fileStream = uploadedFile.OpenReadStream();

                var uploadParams = new ImageUploadParams
                {
                    File = new FileDescription(uploadedFile.FileName, fileStream),
                    Transformation = new Transformation().Height(500).Width(500).Crop("fill").Gravity("face")
                };

                uploadResult = await _cloudinary.UploadAsync(uploadParams);
            }

            return uploadResult;
        }

public async Task<ImageUploadResult> AddPhotoAsync(IFormFile uploadedFile)
        {
            var uploadResult = new ImageUploadResult();

            if (uploadedFile.Length > 0)
            {
                using var fileStream = uploadedFile.OpenReadStream();

                var uploadParams = new ImageUploadParams
                {
                    File = new FileDescription(uploadedFile.FileName, fileStream),
                    Transformation = new Transformation().Height(500).Width(500).Crop("fill").Gravity("face")
                };

                uploadResult = await _cloudinary.UploadAsync(uploadParams);
            }

            return uploadResult;
        }

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

Candyroll93OP•2y ago

Candyroll93OP•2y ago

it looks like _photoService is null

cap5lut•2y ago

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

Candyroll93OP•2y ago

Candyroll93OP•2y ago

this is something im new to.

cap5lut•2y ago

u also need to register the service:

using DependencyInjectionSample.Interfaces;
using DependencyInjectionSample.Services;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();

builder.Services.AddScoped<IMyDependency, MyDependency>(); // like this

var app = builder.Build();

using DependencyInjectionSample.Interfaces;
using DependencyInjectionSample.Services;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();

builder.Services.AddScoped<IMyDependency, MyDependency>(); // like this

var app = builder.Build();

(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.

MODiX•2y ago

To post C# code type the following: ```cs // code here ``` Get an example by typing $codegif in chat If your code is too long, post it to: https://paste.mod.gg/

Candyroll93OP•2y ago

aha! tyvm let me add that in.

cap5lut•2y ago

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

Candyroll93OP•2y ago

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

cap5lut•2y ago

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

Candyroll93OP•2y ago

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

cap5lut•2y ago

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

Candyroll93OP•2y ago

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•2y ago

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)

Candyroll93OP•2y ago

properties as in this?

 private readonly IClubRepository _clubRepository;
        private readonly IPhotoService _photoService;

 private readonly IClubRepository _clubRepository;
        private readonly IPhotoService _photoService;

cap5lut•2y ago

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

Candyroll93OP•2y ago

oooohhhhh i got a different error! we're in business. thats a topic i've yet to discover

cap5lut•2y ago

note that there are 3 different methods on how u can register a service AddSingleton<TInterface, TImplementation>() -> one instance for all which require the TInterface AddTransient<TInterface, TImplementation>() -> everthing gets its own instance AddScoped<TInterface, TImplementation>() -> one instance per scope (asp creates a scope for each incoming request) with properties u can add functionality to accessing the data:

private int _someEvenValue = 0;
public int SomeEvenValue
{
  get
  {
    Console.WriteLine("Reading SomeValue");
    return _someValue;
  }
  set
  {
    if (value % 2 != 0) throw new ArgumentException("Value must be even!");
    _someValue = value;
  }
}

private int _someEvenValue = 0;
public int SomeEvenValue
{
  get
  {
    Console.WriteLine("Reading SomeValue");
    return _someValue;
  }
  set
  {
    if (value % 2 != 0) throw new ArgumentException("Value must be even!");
    _someValue = value;
  }
}

of course there is a lot more to properties, but explaining that all here would take too long ;p cant help ya if u dont give information about it, but ofc its better to try to fix it urself ;p

Candyroll93OP•2y ago

okay thank you very much. i greatly appreciate this. yes once i got a different error, i waws successful in fixing it.

Candyroll93OP•2y ago

it works now