请求和处理包含文件作为byte []的Web-API响应的最佳方法？

Question

我试图从我的REST API返回一个pdf文件,并将ReportController添加到我的控制器集合中,如下所示.

public class ReportController : ApiController
{
    public HttpResponseMessage Get(int id)
    {
        var result = new HttpResponseMessage(HttpStatusCode.OK);
        string fileName = id.ToString();

        MemoryStream memoryStream = GetStreamFromBlob(fileName);
        result.Content = new ByteArrayContent(memoryStream.ToArray());
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");

        return result;
    }
}

其他控制器都可以正常工作,但这是第一个设置为返回HttpResponseMessage而不是可序列化对象或对象集合的控制器.

但是我很难从客户端消费这个.已经尝试了许多版本的代码来执行此操作,但是控制器代码永远不会受到影响,并且似乎很少有成功的方法来调用它.以下是我目前的版本: -

public async Task<string> GetPdfFile(int id)
{
    string fileName = string.Format("C:\\Code\\PDF_Client\\{0}.pdf", id);

    using (HttpClient proxy = new HttpClient())
    {
        string url = string.Format("http://localhost:10056/api/report/{0}", id);
        HttpResponseMessage reportResponse = await proxy.GetAsync(url);  //****
        byte[] b = await reportResponse.Content.ReadAsByteArrayAsync();
        System.IO.File.WriteAllBytes(fileName, b);
    }
    return fileName;
}

但是该行****失败并显示消息No connection could be made because the target machine actively refused it 127.0.0.1:10056.

正如我所说,其他控制器在http://localhost:10056/api/工作正常.

这是从WEBAPI服务器方法获取文件的正确方法吗？

您是否对代码中可能更好的其他区域有任何建议,例如使用await/async,或者控制器返回文件的更好方法？

Answer 1

我遇到了同样的问题,希望将PDF写入ApiController动作的输出.

这个链接帮助我:http://www.asp.net/web-api/overview/formats-and-model-binding/media-formatters

我编写了自己的MediaTypeFormatter,用于从字节数组中编写PDF.

public class PdfFormatter : MediaTypeFormatter
{
    #region Constants and Fields

    private const int ChunkSizeMax = 1024 * 10;

    #endregion

    #region Constructors and Destructors

    public PdfFormatter()
    {
        SupportedMediaTypes.Add(MediaTypeHeaderValue.Parse("application/pdf"));
    }

    #endregion

    #region Public Methods

    public override bool CanReadType(Type type)
    {
        return false; // can't read any types
    }

    public override bool CanWriteType(Type type)
    {
        return type == typeof(byte[]);
    }

    public override Task WriteToStreamAsync(
        Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
    {
        Task t = new Task(() => WritePdfBytes(value, writeStream));
        t.Start();
        return t;
    }

    #endregion

    #region Methods

    private static void WritePdfBytes(object value, Stream writeStream)
    {
        byte[] buffer = value as byte[];
        int offset = 0;

        while (offset < buffer.Length)
        {
            int chunkSize = Math.Min(buffer.Length - offset, ChunkSizeMax);
            writeStream.Write(buffer, offset, chunkSize);
            offset += chunkSize;
        }
    }

    #endregion
}

然后,我在Global.asax中注册了这个格式化程序,如下所示:

private void SetupFormatters()
{
    GlobalConfiguration.Configuration.Formatters.Add(new PdfFormatter());
}

我的ApiController Get方法的相关部分如下所示:

public HttpResponseMessage Get(string url, string title)
{
    byte[] pdfBytes;

    /* generate the pdf into pdfBytes */

    string cleanTitle = new Regex(@"[^\w\d_-]+").Replace(title, "_");
    string contentDisposition = string.Concat("attachment; filename=", cleanTitle, ".pdf");
    HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, pdfBytes, MediaTypeHeaderValue.Parse("application/pdf"));
    response.Content.Headers.ContentDisposition = ContentDispositionHeaderValue.Parse(contentDisposition);

    return response;
}