Post multipart/form-data 来自带有 HttpClient 的流的文件

Question

问题：是否可以使用 httpclient 将 HttpPostedFileBase（仅在内存中可用，在磁盘上不可用。）post 到另一个端点？

我试过的：

我有以下控制器，我们正在 post 从我们的前端输入一个文件，它绑定到文件参数。

public class HomeController : Controller
{
    [System.Web.Http.HttpPost]
    public async Task<string> Index(HttpPostedFileBase file)
    {
        //file is not null here, everything works as it should.

        //Here im preparing a multipart/form-data request to my api endpoint
        var fileStreamContent = new StreamContent(file.InputStream);
        using (var client = new HttpClient())
        using (var formData = new MultipartFormDataContent())
        {
            formData.Add(fileStreamContent);
            var response = await client.PostAsync("http://restapi.dev/api/files/add", formData);
            var result = await response.Content.ReadAsStringAsync();
            return result;
        }
    }
}

我需要将这个请求传递给另一个不公开的应用程序（所以我们不能 post 直接从客户端）该控制器看起来像这样：

[RoutePrefix("api/files")]
public class FilesController : ApiController
{
    [HttpPost]
    [Route("add")]
    public async Task<HttpResponseMessage> Add(HttpPostedFileBase file)
    {
        //This is the problem, file is always null when I post from my backend.
        var files = HttpContext.Current.Request.Files.Count > 0 ? HttpContext.Current.Request.Files[0] : null;
        return Request.CreateResponse(HttpStatusCode.OK);
    }
}

file 始终为空，files 也是。我错过了什么？当我将 postman 和 post 直接用于 API 端点时，它起作用了。所以我猜我在 HomeController?

中做错了什么

Answer 1

您可以使用更新的技术对此进行改进。

在webapi中，你可以这样写一个controller方法：

//[Route("api/Foo")] //maybe?
[HttpPost]
public async Task<HttpResponseMessage> MyResourceProxy(HttpRequestMessage request)

现在您可以接受该请求并重写其 RequestUri 属性:

request.RequestUri = new Uri(blah);

新建一个HttpClient并转发请求：

HttpClient client = new HttpClient();
//make sure that this fails if it's hung for more than 30 seconds
var cts = new CancellationTokenSource(TimeSpan.FromSeconds(30));
try
{
    response = await client.SendAsync(request,
                                      HttpCompletionOption.ResponseHeadersRead, 
                                      cts.Token);
}
catch (TaskCanceledException)
{
    response = new HttpResponseMessage(HttpStatusCode.GatewayTimeout);
}

确保所有东西都得到处理：

request.RegisterForDispose(new IDisposable[] {request, client, cts, response});

然后 return response

return response;

我添加了一个超时机制，可能不适合您的需要。

Post multipart/form-data 来自带有 HttpClient 的流的文件

Post multipart/form-data file from stream with HttpClient

c#

multipartform-data