Return file from ASP.NET 5 Web API

Question

My previous question: How to return file from ASP.net 5 web api

I am trying to return a file as the response from Web API POST request.

I'm using dnx451 framework and rc1-final build. Controller method:

[HttpPost("")]
public ActionResult Post([FromBody]DocumentViewModel vm)
{
    try
    {
        if (ModelState.IsValid)
        {

            var Document = _repository.GetDocumentByGuid(vm.DocumentGuid, User.Identity.Name);
            var Params = Helper.ClientInputToRealValues(vm.Parameters, Document.DataFields);
            var file = Helper.GeneratePdf(Helper.InsertValues(Params, Document.Content));
            FileStream stream = new FileStream(file,FileMode.Open);

            return File(stream, "application/pdf", "test.pdf");

        }

    }
    catch (Exception ex)
    {
        Response.StatusCode = (int)HttpStatusCode.BadRequest;
        return null;
    }
    Response.StatusCode = (int)HttpStatusCode.BadRequest;
    return null;

}

As result I get a file with name "response". After saving it as pdf i try to open it, and it says it is damaged. Hope you can help me. I am using Postman as test client.

Thanks

When you debug this, does the code reach the return File() line? What is the content and headers received in the response? — David
– David, Commented Jan 18, 2016 at 14:38
Is your Helper.GeneratePdf() line doing its work correctly? What is the value of file? Can the file be opened, and did you inspected the file being generated before sending it back to the browser? — Leonardo Herrera
– Leonardo Herrera, Commented Jan 18, 2016 at 14:47
yes the pdf is generated, and I can open generated pdf file from File explorer and it is just fine. — Joonas Püüa
– Joonas Püüa, Commented Jan 18, 2016 at 14:48

Community · Accepted Answer · 2017-05-23 11:33:14Z

25

Please see my answer in the other post: Return file as response

For reference, I think this fits your needs:

public FileResult TestDownload()
{
    HttpContext.Response.ContentType = "application/pdf";
    FileContentResult result = new FileContentResult(System.IO.File.ReadAllBytes("YOUR PATH TO PDF"), "application/pdf")
    {
        FileDownloadName = "test.pdf"
    };

    return result;                                
}

edited May 23, 2017 at 11:33

CommunityBot

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answered Jan 18, 2016 at 14:28

Ian Auty

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8 Comments

Joonas Püüa Over a year ago

The result is still the same. Response returns file called "response". if i rename it to somthing.pdf and try to open it - it is still damaged.

Ian Auty Over a year ago

I have tested that code locally with a local pdf and the file downloaded properly and I could open it. Is the pdf path local to your machine, or are you generating it dynamically or something? Where I've stated 'YOUR PATH TO PDF', you must include the extension also.

Joonas Püüa Over a year ago

basically I am creating it but atm I am testing with local file. yes .pdf is included. I think it could be PostMan issue.

Ian Auty Over a year ago

Quite possibly, to confirm the code works for you with your PDF you could create a new MVC project and just add that method to the HomeController.cs that's generated for you. That's what I did to test before posting. Then you can find out the culprit from there :)

Boanerge Over a year ago

FileResult and FileContentResult are Mvc classes, that's not Webapi

|

Mark Rendle · Accepted Answer · 2016-05-30 20:25:39Z

I've just had this problem and found a solution. As long as you have an absolute path to your file, then you can return a PhysicalFileResult and explicitly set the Content-Disposition header on the Response, like so:

[HttpGet("{key}")]
public IActionResult Get(string key)
{
    var file = _files.GetPath(key);

    var result = PhysicalFile(file.Path, "text/text");

    Response.Headers["Content-Disposition"] = new ContentDispositionHeaderValue("attachment")
    {
        FileName = file.Name
    }.ToString();

    return result;
}

Using PhysicalFile also has the advantage that all the asynchronous streaming of bytes and so on is taken care of by the framework.

Jnr · Accepted Answer · 2022-01-16 03:43:47Z

It's perhaps better to consider the use the FileStreamResult action result.

This has the advantage of not requiring that the entire file contents be held in memory which, depending on the size of the file, level of traffic, etc. could very easily lead to problems of scale.

Something like this:

[HttpGet]
public FileStreamResult DownloadFile()
{
    var Document = _repository.GetDocumentByGuid(vm.DocumentGuid, User.Identity.Name);
    var Params = Helper.ClientInputToRealValues(vm.Parameters, Document.DataFields);
    var file = Helper.GeneratePdf(Helper.InsertValues(Params, Document.Content));
    var stream = new FileStream(file,FileMode.Open);
    return new FileStreamResult(stream, "application/pdf")
    {
        FileDownloadName = "test.pdf"
    };
}

This requires importing System.Web.Mvc, which will break everything else in a WebAPI controller. The question was about WebAPI.

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