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

A relatively easy way to achieve this is to use the built-in PhysicalFile result, which is available to all controllers: MS Docs: PhysicalFile

A simple example:

public IActionResult DownloadFile(string filePath)
{
     return PhysicalFile(filePath, MimeTypes.GetMimeType(filePath), Path.GetFileName(filePath));
}

Now of course you should never expose this kind of API, due to security concerns.

I typically shield the actual file paths behind a friendly identifier, which I then use to lookup the real file path (or return a 404 if an invalid ID was passed in), ie:

[HttpGet("download-file/{fileId}")]
public IActionResult DownloadFile(int fileId)
{
    var filePath = GetFilePathFromId(fileId);
    if (filePath == null) return NotFound();

    return PhysicalFile(filePath, MimeTypes.GetMimeType(filePath), Path.GetFileName(filePath));
}

For those that are curious, the MimeTypes helper is a great little nuget package from the folks at MimeKit