如何返回一个文件(FileContentResult)在ASP。净WebAPI

在常规的MVC控制器中，我们可以输出带有FileContentResult的pdf。

public FileContentResult Test(TestViewModel vm)
{
    var stream = new MemoryStream();
    //... add content to the stream.

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

但是我们如何把它变成ApiController呢?

[HttpPost]
public IHttpActionResult Test(TestViewModel vm)
{
     //...
     return Ok(pdfOutput);
}

这是我试过的方法，但似乎不管用。

[HttpGet]
public IHttpActionResult Test()
{
    var stream = new MemoryStream();
    //...
    var content = new StreamContent(stream);
    content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
    content.Headers.ContentLength = stream.GetBuffer().Length;
    return Ok(content);            
}

在浏览器中返回的结果为:

{"Headers":[{"Key":"Content-Type","Value":["application/pdf"]},{"Key":"Content-Length","Value":["152844"]}]}

还有一篇类似的关于SO的文章:在ASP中从控制器返回二进制文件。NET Web API 。它讨论的是输出一个现有文件。但是我不能让它在溪流中工作。

有什么建议吗?

当前回答

如果你想返回IHttpActionResult，你可以这样做:

[HttpGet]
public IHttpActionResult Test()
{
    var stream = new MemoryStream();

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new ByteArrayContent(stream.GetBuffer())
    };
    result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
    {
        FileName = "test.pdf"
    };
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

    var response = ResponseMessage(result);

    return response;
}

2016-05-26 07:41:47

其他回答

我不太确定是哪一部分的问题，但这就是为什么MemoryStream不适合你:

当你写入MemoryStream时，它会增加它的Position属性。 StreamContent的构造函数会考虑流的当前位置。因此，如果您写入流，然后将其传递给StreamContent，响应将从流末尾的虚无开始。

有两种方法可以正确解决这个问题:

construct content, write to stream [HttpGet] public HttpResponseMessage Test() { var stream = new MemoryStream(); var response = Request.CreateResponse(HttpStatusCode.OK); response.Content = new StreamContent(stream); // ... // stream.Write(...); // ... return response; } write to stream, reset position, construct content [HttpGet] public HttpResponseMessage Test() { var stream = new MemoryStream(); // ... // stream.Write(...); // ... stream.Position = 0; var response = Request.CreateResponse(HttpStatusCode.OK); response.Content = new StreamContent(stream); return response; } looks a little better if you have a fresh Stream, 1) is simpler if your stream does not start at 0

2016-05-19 13:29:17

这里是一个不缓冲文件内容的流输出实现(如果它是一个大文件，缓冲在byte[] / MemoryStream等中可能是一个服务器问题)。

public class FileResult : IHttpActionResult
{
    public FileResult(string filePath)
    {
        if (filePath == null)
            throw new ArgumentNullException(nameof(filePath));

        FilePath = filePath;
    }

    public string FilePath { get; }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        var response = new HttpResponseMessage(HttpStatusCode.OK);
        response.Content = new StreamContent(File.OpenRead(FilePath));
        var contentType = MimeMapping.GetMimeMapping(Path.GetExtension(FilePath));
        response.Content.Headers.ContentType = new MediaTypeHeaderValue(contentType);
        return Task.FromResult(response);
    }
}

它可以这样简单地使用:

public class MyController : ApiController
{
    public IHttpActionResult Get()
    {
        string filePath = GetSomeValidFilePath();
        return new FileResult(filePath);
    }
}

2018-10-24 15:53:58

 var memoryStream = new MemoryStream();
                await cloudFile.DownloadToStreamAsync(memoryStream);
                responseMessage.result = "Success";

                var contentType = "application/octet-stream";
            
                **using (var stream = new MemoryStream())
                {                    
                    return File(memoryStream.GetBuffer(), contentType, "Cartage.pdf");
                }**

2021-08-28 14:03:13

而不是返回StreamContent作为内容，我可以使它与ByteArrayContent一起工作。

[HttpGet]
public HttpResponseMessage Generate()
{
    var stream = new MemoryStream();
    // processing the stream.

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new ByteArrayContent(stream.ToArray())
    };
    result.Content.Headers.ContentDisposition =
        new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
    {
        FileName = "CertificationCard.pdf"
    };
    result.Content.Headers.ContentType =
        new MediaTypeHeaderValue("application/octet-stream");

    return result;
}

2014-09-25 14:34:45

如果你想返回IHttpActionResult，你可以这样做:

[HttpGet]
public IHttpActionResult Test()
{
    var stream = new MemoryStream();

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new ByteArrayContent(stream.GetBuffer())
    };
    result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
    {
        FileName = "test.pdf"
    };
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

    var response = ResponseMessage(result);

    return response;
}

2016-05-26 07:41:47

如何返回一个文件(FileContentResult)在ASP。净WebAPI

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