无法解决服务

Question

我正在设计一个使用 ASP.net MVC 和 ASP.NET Wep API 上传和下载文件的个人网站。

我收到此错误 " InvalidOperationException：尝试激活“ProjectsApp.Controllers.FilesController”时无法解析“Microsoft.Extensions.FileProviders.IFileProvider”类型的服务。 Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired) "

这是我的 startup.cs 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.UI;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Session;
using Microsoft.EntityFrameworkCore;
using ProjectsApp.Data;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace ProjectsApp
{
  public class Startup
  {
    public Startup(IConfiguration configuration)
    {
      Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
      services.Configure<CookiePolicyOptions>(options =>
      {
        // This lambda determines whether user consent for non-essential cookies is needed for a given request.
        options.CheckConsentNeeded = context => true;
        options.MinimumSameSitePolicy = SameSiteMode.None;
      });

      services.AddDbContext<ApplicationDbContext>(options =>
          options.UseSqlServer(
              Configuration.GetConnectionString("DefaultConnection")));
            services.AddIdentity<IdentityUser, IdentityRole>().AddDefaultUI(UIFramework.Bootstrap4)
          .AddEntityFrameworkStores<ApplicationDbContext>().AddSignInManager<SignInManager<IdentityUser>>().AddDefaultTokenProviders();
            //services.AddDefaultIdentity<IdentityUser>()
            //.AddDefaultUI(UIFramework.Bootstrap4)
            //.AddEntityFrameworkStores<ApplicationDbContext>();
    
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

      // These components support HttpContext.Session

      services.AddMvc().AddCookieTempDataProvider();
      services.AddDistributedMemoryCache();
      services.AddSession(options =>
      {
        options.IdleTimeout = TimeSpan.FromMinutes(20);
        options.Cookie.HttpOnly = false;
        options.Cookie.IsEssential = true;
      });

    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
      if (env.IsDevelopment())
      {
        app.UseDeveloperExceptionPage();
        app.UseDatabaseErrorPage();
      }
      else
      {
        app.UseExceptionHandler("/Home/Error");
        // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
        app.UseHsts();
      }

      app.UseHttpsRedirection();
      app.UseStaticFiles();
      app.UseAuthentication();
      app.UseCookiePolicy();
      app.UseSession();

      app.UseMvc(routes =>
      {
        routes.MapRoute(
                  name: "default",
                  template: "{controller=Home}/{action=Index}/{id?}");
      });
    }
  }

这是我的文件控制器

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Http;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.IO;
using ProjectsApp.Models;
using Microsoft.Extensions.FileProviders;


namespace ProjectsApp.Controllers
{
    public class FilesController : Controller
    {
        private readonly IFileProvider fileProvider;

        public FilesController(IFileProvider fileProvider)
        {
            this.fileProvider = fileProvider;
        }

        public IActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> UploadFile(IFormFile file)
        {
            if (file == null || file.Length == 0)
                return Content("file not selected");

            var path = Path.Combine(
                        Directory.GetCurrentDirectory(), "wwwroot",
                        file.GetFilename());

            using (var stream = new FileStream(path, FileMode.Create))
            {
                await file.CopyToAsync(stream);
            }

            return RedirectToAction("Files");
        }

        [HttpPost]
        public async Task<IActionResult> UploadFiles(List<IFormFile> files)
        {
            if (files == null || files.Count == 0)
                return Content("files not selected");

            foreach (var file in files)
            {
                var path = Path.Combine(
                        Directory.GetCurrentDirectory(), "wwwroot",
                        file.GetFilename());

                using (var stream = new FileStream(path, FileMode.Create))
                {
                    await file.CopyToAsync(stream);
                }
            }

            return RedirectToAction("Files");
        }

        [HttpPost]
        public async Task<IActionResult> UploadFileViaModel(FileInputModel model)
        {
            if (model == null ||
                model.FileToUpload == null || model.FileToUpload.Length == 0)
                return Content("file not selected");

            var path = Path.Combine(
                        Directory.GetCurrentDirectory(), "wwwroot",
                        model.FileToUpload.GetFilename());

            using (var stream = new FileStream(path, FileMode.Create))
            {
                await model.FileToUpload.CopyToAsync(stream);
            }

            return RedirectToAction("Files");
        }

        public IActionResult Files()
        {
            var model = new FilesViewModel();
            foreach (var item in this.fileProvider.GetDirectoryContents(""))
            {
                model.Files.Add(
                    new FileDetails { Name = item.Name, Path = item.PhysicalPath });
            }
            return View(model);
        }

        public async Task<IActionResult> Download(string filename)
        {
            if (filename == null)
                return Content("filename not present");

            var path = Path.Combine(
                           Directory.GetCurrentDirectory(),
                           "wwwroot", filename);

            var memory = new MemoryStream();
            using (var stream = new FileStream(path, FileMode.Open))
            {
                await stream.CopyToAsync(memory);
            }
            memory.Position = 0;
            return File(memory, GetContentType(path), Path.GetFileName(path));
        }

        private string GetContentType(string path)
        {
            var types = GetMimeTypes();
            var ext = Path.GetExtension(path).ToLowerInvariant();
            return types[ext];
        }

        private Dictionary<string, string> GetMimeTypes()
        {
            return new Dictionary<string, string>
            {
                {".txt", "text/plain"},
                {".pdf", "application/pdf"},
                {".doc", "application/vnd.ms-word"},
                {".docx", "application/vnd.ms-word"},
                {".xls", "application/vnd.ms-excel"},
                {".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
                {".png", "image/png"},
                {".jpg", "image/jpeg"},
                {".jpeg", "image/jpeg"},
                {".gif", "image/gif"},
                {".csv", "text/csv"}
            };
        }
    }
}

谢谢！

Answer 1

您需要在 ConfigureServices 中将 file provider 注册为服务。或者拥有自己的实现IFileProvider 接口的文件提供程序类并注册它。

有一个example 介绍如何使用文件提供程序。

Answer 2

假设您在 Startup 类中有 private IHostingEnvironment _hostingEnvironment;。

将构造函数更改为

public Startup(IHostingEnvironment env, IConfiguration config, 
        ILoggerFactory loggerFactory)
    {
        _hostingEnvironment= env;
        _config = config;
        _loggerFactory = loggerFactory;
    }

在 ConfigureServices() 方法的末尾添加这个

var physicalProvider = _hostingEnvironment.ContentRootFileProvider;
var embeddedProvider = new EmbeddedFileProvider(Assembly.GetEntryAssembly());
var compositeProvider = new CompositeFileProvider(physicalProvider, embeddedProvider);

// choose one provider to use for the app and register it

services.AddSingleton<IFileProvider>(compositeProvider);