如何在ASP.NET WebAPI中返回文件(FileContentResult)

我可以让它与ByteArrayContent一起工作，而不是将StreamContent返回为Content。

[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;
}

如果您想返回IHttpActionResult，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;
}

这个问题帮助了我。

所以，试试这个：

控制器代码：

[HttpGet]
public HttpResponseMessage Test()
{
    var path = System.Web.HttpContext.Current.Server.MapPath("~/Content/test.docx");;
    HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
    var stream = new FileStream(path, FileMode.Open);
    result.Content = new StreamContent(stream);
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
    result.Content.Headers.ContentDisposition.FileName = Path.GetFileName(path);
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
    result.Content.Headers.ContentLength = stream.Length;
    return result;          
}

查看Html标记（带有点击事件和简单url）：

<script type="text/javascript">
    $(document).ready(function () {
        $("#btn").click(function () {
            // httproute = "" - using this to construct proper web api links.
            window.location.href = "@Url.Action("GetFile", "Data", new { httproute = "" })";
        });
    });
</script>

<button id="btn">
    Button text
</button>
<a href=" @Url.Action("GetFile", "Data", new { httproute = "" }) ">Data</a>

这里有一个实现，它可以在不缓冲文件的情况下将文件的内容流式传输出去（如果是大文件，则以byte[]/MemoryStream等缓冲可能是服务器问题）。

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);
    }
}

它可以简单地这样使用：

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

我不确定该归咎于哪一部分，但以下是MemoryStream不适用于您的原因：

当您向MemoryStream写入时，它会递增其Position属性。CCD_ 10的构造函数考虑流的当前CCD_。因此，如果您写入流，然后将其传递给StreamContent，则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：

1. 构建内容，写入流

    [HttpGet]
    public HttpResponseMessage Test()
    {
        var stream = new MemoryStream();
        var response = Request.CreateResponse(HttpStatusCode.OK);
        response.Content = new StreamContent(stream);
        // ...
        // stream.Write(...);
        // ...
        return response;
    }
   

2. 写入流，重置位置，构建内容

    [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;
    }
   

3. 如果你有一个新的流，看起来会更好，1）如果你的流不是从0 开始，会更简单

对我来说，这是之间的区别

var response = Request.CreateResponse(HttpStatusCode.OK, new StringContent(log, System.Text.Encoding.UTF8, "application/octet-stream");

和

var response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StringContent(log, System.Text.Encoding.UTF8, "application/octet-stream");

第一个是返回StringContent的JSON表示：｛"Headers"：[｛"Key"："Content Type"，"Value"：["application/octet stream；charset=utf-8"]｝｝

而第二个正在返回正确的文件。

Request.CreateResponse似乎有一个重载，它将字符串作为第二个参数，这似乎是导致StringContent对象本身被呈现为字符串而不是实际内容的原因。

我发现这篇文章很有用：https://codeburst.io/download-files-using-web-api-ae1d1025f0a9

基本上说：

[Route("api/[controller]")]
[ApiController]
public class JobController : ControllerBase
{
    [HttpGet]
    public ActionResult GetFile()
    {
        byte[] fileContent = GetFile();
        return File(fileContent, "application/pdf", "test.pdf");
    }
}

 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");
                }**