向项目添加文件上传功能时遇到问题 - ASP.Net MVC Core 3.0

Question

Please forgive me if I forgot some key piece of information, I am a pretty new developer and this is my first posting.

I am attempting to add a feature to my ASP.Net MVC 5 Core 3 project where the user can upload a file to ~/wwwroot/PromotionImages but I am having trouble finding many resources for Core 3.0

Best solution is probably to start over using an older version of Core where I will find more resources, but I am pretty far into this project already.

I have read that MapPath no longer works in Core 3, but I am not really sure what replaces it. WebRootPath is a property of IWebHostEnvironment but I'm not sure how to implement that.

I receive the following three errors that I haven't been able to work through.

CS1061  'IWebHostEnvironment' does not contain a definition for 'MapPath' and no accessible extension method 'MapPath' accepting a first argument of type 'IWebHostEnvironment' could be found (are you missing a using directive or an assembly reference?)

CS0119  'ControllerBase.File(byte[], string)' is a method, which is not valid in the given context

CS0103  The name 'FileMode' does not exist in the current context

Startup.cs

public class Startup
    {
        public Startup(IConfiguration configuration, IWebHostEnvironment environment)
        {
            Configuration = configuration;
            this.Environment = environment;
        }

        public IConfiguration Configuration { get; }
        public IWebHostEnvironment Environment { get; }

PromotionsController.cs

public class PromotionsController : Controller
    {

        private readonly IWebHostEnvironment hostingEnvironment;
        private readonly MonitorContext _context;

        public PromotionsController(MonitorContext context, IWebHostEnvironment hostingEnvironment)
        {
            _context = context;
            this.hostingEnvironment = hostingEnvironment;
        }

[HttpPost]
[ValidateAntiForgeryToken]

        public async Task<IActionResult> Create([Bind("PromoId,MonitorId,PromoTitle,PromoPath")] Promotion promotion)
        {
            if (ModelState.IsValid)
            {
                var relativeWebPath = $"/PromotionImages/{promotion.PromoFile.FileName}";
                var filePath = this.hostingEnvironment.MapPath($"~/wwwroot/{relativeWebPath}");
                using (var fileStream = File.Open(filePath, FileMode.OpenOrCreate))
                {
                    promotion.PromoFile.CopyTo(fileStream);
                }
                promotion.PromoPath = relativeWebPath;

                _context.Add(promotion);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View(promotion);
        }

Answer 1

For map path, you can use the System.IO.Path class. Here is some code which can be the starting point.

View code

<form method="post" enctype="multipart/form-data">
    <input type="File" name="file" />
    <input type="submit" value="Upload" />
</form>

And here is the controller code.

[HttpPost]
public IActionResult Index(IFormFile file)
{
    var imagePath = Path.Combine(_hostEnvironment.WebRootPath, "images");

    var uploadedFileExtn = Path.GetExtension(file.FileName);
    var fileName = Path.ChangeExtension(Guid.NewGuid().ToString("N"), uploadedFileExtn);
    using (var stream = System.IO.File.OpenWrite(Path.Combine(imagePath, fileName)))
    {
        file.CopyTo(stream);
    }

    return View();
}

First I am creating the path of the images folder. Next, I am looking for the file extension. Then I am generating a unique file name with the extension and saving the file.