How to download a file in ASP.NET Core

Question

In MVC, we have used following code to download a file. In ASP.NET core, how to achieve this?

HttpResponse response = HttpContext.Current.Response;                   


        

Answer 1

    [HttpGet]
    public async Task<FileStreamResult> Download(string url, string name, string contentType)
    {
        var stream = await new HttpClient().GetStreamAsync(url);

        return new FileStreamResult(stream, contentType)
        {
            FileDownloadName = name,
        };
    }

Answer 2

Action method needs to return FileResult with either a stream, byte[], or virtual path of the file. You will also need to know the content-type of the file being downloaded. Here is a sample (quick/dirty) utility method. Sample video link How to download files using asp.net core

[Route("api/[controller]")]
public class DownloadController : Controller
{
    [HttpGet]
    public async Task<IActionResult> Download()
    {
        var path = @"C:\Vetrivel\winforms.png";
        var memory = new MemoryStream();
        using (var stream = new FileStream(path, FileMode.Open))
        {
            await stream.CopyToAsync(memory);
        }
        memory.Position = 0;
        var ext = Path.GetExtension(path).ToLowerInvariant();
        return File(memory, GetMimeTypes()[ext], Path.GetFileName(path));
    }

    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"},
            {".png", "image/png"},
            {".jpg", "image/jpeg"},
            ...
        };
    }
}

Answer 3

Create a Service say FileService.

public class FileService
{
    private readonly IHostingEnvironment _hostingEnvironment;
    constructor(IHostingEnvironment hostingEnvironment)
    {
        this._hostingEnvironment = hostingEnvironment;
    }
}

Add a method to FileService MimeType of the file

private string GetMimeType(string fileName)
{
    // Make Sure Microsoft.AspNetCore.StaticFiles Nuget Package is installed
    var provider = new FileExtensionContentTypeProvider();
    string contentType;
    if (!provider.TryGetContentType(fileName, out contentType))
    {
        contentType = "application/octet-stream";
    }
    return contentType;
}

Now add a method to download File,

public FileContentResult GetFile(string filename) 
{
    var filepath = Path.Combine($"{this._environment.WebRootPath}\\path-to-required-folder\\{filename}");

    var mimeType = this.GetMimeType(filename); 

    byte[] fileBytes;

    if (File.Exists(filepath))
    {
        fileBytes = File.ReadAllBytes(filepath); 
    } 
    else
    {
        // Code to handle if file is not present
    }

    return new FileContentResult(fileBytes, mimeType)
    {
        FileDownloadName = filename
    };
}

Now add controller method and call GetFile method in FileService,

 public IActionResult DownloadFile(string filename) 
 {
    // call GetFile Method in service and return       
 }

Answer 4

Example for Asp.net Core 2.1+ (Best practice)

Startup.cs:

private readonly IHostingEnvironment _env;

public Startup(IConfiguration configuration, IHostingEnvironment env)
{
    Configuration = configuration;
    _env = env;
}

services.AddSingleton(_env.ContentRootFileProvider); //Inject IFileProvider

SomeService.cs:

private readonly IFileProvider _fileProvider;

public SomeService(IFileProvider fileProvider)
{
    _fileProvider = fileProvider;
}

public FileStreamResult GetFileAsStream()
{
    var stream = _fileProvider
        .GetFileInfo("RELATIVE PATH TO FILE FROM APP ROOT")
        .CreateReadStream();

    return new FileStreamResult(stream, "CONTENT-TYPE")
}

Controller will return IActionResult

[HttpGet]
public IActionResult Get()
{
    return _someService.GetFileAsStream() ?? (IActionResult)NotFound();
}

Answer 5

You can try below code to download the file. It should return the FileResult

public ActionResult DownloadDocument()
{
string filePath = "your file path";
string fileName = ""your file name;

byte[] fileBytes = System.IO.File.ReadAllBytes(filePath);

return File(fileBytes, "application/force-download", fileName);

}

Answer 6

Here is my Medium article, describing everything step by step (it also includes a GitHub repo): https://medium.com/@tsafadi/download-a-file-with-asp-net-core-e23e8b198f74

Any ways this is how the controller should look like:

[HttpGet]
public IActionResult DownloadFile()
{
    // Since this is just and example, I am using a local file located inside wwwroot
    // Afterwards file is converted into a stream
    var path = Path.Combine(_hostingEnvironment.WebRootPath, "Sample.xlsx");
    var fs = new FileStream(path, FileMode.Open);

    // Return the file. A byte array can also be used instead of a stream
    return File(fs, "application/octet-stream", "Sample.xlsx");
}

Inside the view:

$("button").click(function () {
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "Download/DownloadFile", true);
    xhr.responseType = "blob";
    xhr.onload = function (e) {
        if (this.status == 200) {
            var blob = this.response;

            /* Get filename from Content-Disposition header */
            var filename = "";
            var disposition = xhr.getResponseHeader('Content-Disposition');
            if (disposition && disposition.indexOf('attachment') !== -1) {
                var filenameRegex = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/;
                var matches = filenameRegex.exec(disposition);
                if (matches != null && matches[1]) filename = matches[1].replace(/['"]/g, '');
            }

            // This does the trick
            var a = document.createElement('a');
            a.href = window.URL.createObjectURL(blob);
            a.download = filename;
            a.dispatchEvent(new MouseEvent('click'));
        }
    }
    xhr.send();
});