C# 如何使用 Web API 返回文件？

How to return a file using Web API?

提问by Kyle

I am using ASP.NET Web API.
I want to download a PDF with C# from the API (that the API generates).

我正在使用ASP.NET Web API。
我想从 API（API 生成）下载带有 C# 的 PDF。

Can I just have the API return a byte[]? and for the C# application can I just do:

我可以让 API 返回一个byte[]吗？对于 C# 应用程序，我可以这样做：

byte[] pdf = client.DownloadData("urlToAPI");? 

and

和

File.WriteAllBytes()?

采纳答案by Regfor

Better to return HttpResponseMessage with StreamContent inside of it.

最好返回包含 StreamContent 的 HttpResponseMessage 。

Here is example:

这是示例：

public HttpResponseMessage GetFile(string id)
{
    if (String.IsNullOrEmpty(id))
        return Request.CreateResponse(HttpStatusCode.BadRequest);

    string fileName;
    string localFilePath;
    int fileSize;

    localFilePath = getFileFromID(id, out fileName, out fileSize);

    HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
    response.Content = new StreamContent(new FileStream(localFilePath, FileMode.Open, FileAccess.Read));
    response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
    response.Content.Headers.ContentDisposition.FileName = fileName;
    response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");

    return response;
}

UPDfrom comment by patridge: Should anyone else get here looking to send out a response from a byte array instead of an actual file, you're going to want to use new ByteArrayContent(someData) instead of StreamContent (see here).

UPD来自patridge 的评论：如果其他人来到这里希望从字节数组而不是实际文件发送响应，您将要使用 new ByteArrayContent(someData) 而不是 StreamContent（请参阅此处）。

回答by André de Mattos Ferraz

I made the follow action:

我做了以下操作：

[HttpGet]
[Route("api/DownloadPdfFile/{id}")]
public HttpResponseMessage DownloadPdfFile(long id)
{
    HttpResponseMessage result = null;
    try
    {
        SQL.File file = db.Files.Where(b => b.ID == id).SingleOrDefault();

        if (file == null)
        {
            result = Request.CreateResponse(HttpStatusCode.Gone);
        }
        else
        {
            // sendo file to client
            byte[] bytes = Convert.FromBase64String(file.pdfBase64);


            result = Request.CreateResponse(HttpStatusCode.OK);
            result.Content = new ByteArrayContent(bytes);
            result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
            result.Content.Headers.ContentDisposition.FileName = file.name + ".pdf";
        }

        return result;
    }
    catch (Exception ex)
    {
        return Request.CreateResponse(HttpStatusCode.Gone);
    }
}

回答by Ogglas

Example with IHttpActionResultin ApiController.

以IHttpActionResultin为例ApiController。

[HttpGet]
[Route("file/{id}/")]
public IHttpActionResult GetFileForCustomer(int id)
{
    if (id == 0)
      return BadRequest();

    var file = GetFile(id);

    IHttpActionResult response;
    HttpResponseMessage responseMsg = new HttpResponseMessage(HttpStatusCode.OK);
    responseMsg.Content = new ByteArrayContent(file.SomeData);
    responseMsg.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
    responseMsg.Content.Headers.ContentDisposition.FileName = file.FileName;
    responseMsg.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
    response = ResponseMessage(responseMsg);
    return response;
}

If you don't want to download the PDF and use a browsers built in PDF viewer instead remove the following two lines:

如果您不想下载 PDF 并使用内置 PDF 查看器的浏览器，请删除以下两行：

responseMsg.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
responseMsg.Content.Headers.ContentDisposition.FileName = file.FileName;

回答by Amir Shirazi

Just a note for .Net Core: We can use the FileContentResultand set the contentType to application/octet-streamif we want to send the raw bytes. Example:

请注意.Net Core：如果我们想发送原始字节，我们可以使用FileContentResult并将 contentType 设置为application/octet-stream。例子：

[HttpGet("{id}")]
public IActionResult GetDocumentBytes(int id)
{
    byte[] byteArray = GetDocumentByteArray(id);
    return new FileContentResult(byteArray, "application/octet-stream");
}

回答by Jake

I've been wondering if there was a simple way to download a file in a more ... "generic" way. I came up with this.

我一直想知道是否有一种简单的方法可以以更......“通用”的方式下载文件。我想出了这个。

It's a simple ActionResultthat will allow you to download a file from a controller call that returns an IHttpActionResult. The file is stored in the byte[] Content. You can turn it into a stream if needs be.

这是一个简单的方法ActionResult，它允许您从返回IHttpActionResult. 该文件存储在byte[] Content. 如果需要，您可以将其转换为流。

I used this to return files stored in a database's varbinary column.

我用它来返回存储在数据库的 varbinary 列中的文件。

    public class FileHttpActionResult : IHttpActionResult
    {
        public HttpRequestMessage Request { get; set; }

        public string FileName { get; set; }
        public string MediaType { get; set; }
        public HttpStatusCode StatusCode { get; set; }

        public byte[] Content { get; set; }

        public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
        {
            HttpResponseMessage response = new HttpResponseMessage(StatusCode);

            response.StatusCode = StatusCode;
            response.Content = new StreamContent(new MemoryStream(Content));
            response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
            response.Content.Headers.ContentDisposition.FileName = FileName;
            response.Content.Headers.ContentType = new MediaTypeHeaderValue(MediaType);

            return Task.FromResult(response);
        }
    }