如何使用Web API返回文件？

Question

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

我可以让 API 返回

byte[]

吗？对于 C# 应用程序我可以这样做吗：

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

和

File.WriteAllBytes()?

Answer 1

最好返回其中包含 StreamContent 的 HttpResponseMessage。

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;
}

更新来自patridge的评论： 如果其他人到达这里希望从字节数组而不是实际文件发送响应，您将需要使用

new ByteArrayContent(someData)

而不是

StreamContent

（请参阅此处）。

Answer 2

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

。示例：

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

Answer 3

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);
    }
}

Answer 4

例如

IHttpActionResult

中的

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;
}

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;

Answer 5

已安装文件下载，可以存入Stream直接传文件下载

 [HttpGet]
    [Route("api/getFile")]
    public async  Task<FileResult> GetFile(string Param1,string Param2)
    {
        try
        {
            Stream stream = null;
            string strURL = @"File URL";
            HttpClient client = new HttpClient();
            HttpResponseMessage httpResponse = await client.GetAsync(strURL);
            Stream streamToReadFrom = await httpResponse.Content.ReadAsStreamAsync();
            return File(streamToReadFrom, "{MIME TYPE}");

        }
        catch (Exception ex)
        {

            throw ex;
        }
        finally
        { 
        
        }
    }

Answer 6

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。

这是一个简单的

ActionResult

，允许您从返回

IHttpActionResult

的控制器调用下载文件。 文件存储在

byte[] Content

中。如果需要，您可以将其转换为流。

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);
        }
    }

Answer 7

下载文件的另一种方法是将流内容直接写入响应的正文中：

[HttpGet("pdfstream/{id}")]
public async Task  GetFile(long id)
{        
    var stream = GetStream(id);
    Response.StatusCode = (int)HttpStatusCode.OK;
    Response.Headers.Add( HeaderNames.ContentDisposition, $"attachment; filename=\"{Guid.NewGuid()}.pdf\"" );
    Response.Headers.Add( HeaderNames.ContentType, "application/pdf"  );            
    await stream.CopyToAsync(Response.Body);
    await Response.Body.FlushAsync();           
}

Answer 8

我的尝试是：

public HttpResponseMessage GetFileFromPath2(string guid)
        {
            var response = new HttpResponseMessage();            
            MemoryStream memoryStream = new MemoryStream();
            var path = "C:\test";
            if (_fileHelper.ExtistFileFromPath(path, guid))
            {
                        memoryStream = new MemoryStream(File.ReadAllBytes(Path.Combine(path, guid)));

                        response.StatusCode = HttpStatusCode.OK;
                        response.Content = new StreamContent(memoryStream);
                        
                        response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = guid };
                        response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
                        response.Headers.AcceptRanges.Add("bytes");
            }
            else
            {
                response.StatusCode = HttpStatusCode.NoContent;
                response.Content = new StringContent("File not found");
            }

            return response;
        }