Upload And Download Files Using ASP.NET Core 2.0

Here, I will explain how to upload and download files in ASP.NET Core 2.0.

First of all create an empty project with ASP.NET Core 2.0 and Update the Startup.cs file to add services and middle ware for MVC.

 public class Startup
 {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton(
                new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), "wwwroot")));
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            app.UseDeveloperExceptionPage();
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Demo}/{action=Index}/{id?}");
            });
        }
 }

Now, Add a Controller with name "DemoController" and copy paste below action methods to upload and download the files.

Include this NameSpaces :

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Http;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.IO;
using Microsoft.Extensions.FileProviders;
using Nikhil.Mvc.FileUpload.Models.Home; // call model folder here


 public class DemoController : Controller
    {
        private readonly IFileProvider fileProvider;

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

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

        [HttpPost]
        public async Task UploadFiles(List 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");
        }

        public async Task 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 GetMimeTypes()
        {
            return new Dictionary
            {
                {".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"}
            };
        }
    }

Create a model class in Model/Demo folder.

1. IFormFileExtensions.cs :

public static class IFormFileExtensions
{
        public static string GetFilename(this IFormFile file)
        {
            return ContentDispositionHeaderValue.Parse(
                            file.ContentDisposition).FileName.ToString().Trim('"');
        }

        public static async Task GetFileStream(this IFormFile file)
        {
            MemoryStream filestream = new MemoryStream();
            await file.CopyToAsync(filestream);
            return filestream;
        }

        public static async Task GetFileArray(this IFormFile file)
        {
            MemoryStream filestream = new MemoryStream();
            await file.CopyToAsync(filestream);
            return filestream.ToArray();
        }
}

2. FilesViewModel.cs :

public class FileDetails
{
        public string Name { get; set; }
        public string Path { get; set; }
}

public class FilesViewModel
{
        public List Files { get; set; } 
            = new List();
}

Now, Add a Razor page with HTML form to upload a file.

1. Index.cshtml :

2. Files.cshtml :

Now, You can able to upload file and download file.