Post files from ASP.NET Core web api to another ASP.NET Core web api

Question

We are building a web application that consist of an Angular2 frontend, a ASP.NET Core web api public backend, and a ASP.NET Core web api private backend.

Uploading files from Angular2 to the public backend works. But we would prefer to post them forward to the private backend.

Current working code

[HttpPost]
public StatusCodeResult Post(IFormFile file)
{
  ...
}

From there I can save the file to disk using file.CopyTo(fileStream);

However, I want to re-send that file, or those files, or, ideally, the whole request to my second web api core.

I am not sure how to achieve this with the HttpClient class of asp.net core.

I've tried all kinds of things such as

StreamContent ss = new StreamContent(HttpContext.Request.Body);
var result = client.PostAsync("api/Values", ss).Result;

But my second backend gets an empty IFormFile.

I have a feeling it is possible to send the file(s) as a stream and reconstruct them on the other side, but can't get it to work.

The solution must use two web api core.

Answer 1

Solution

Public backend in DMZ

[HttpPost]
public StatusCodeResult Post(IFormFile file)
{
    try
    {
        if (file != null && file.Length > 0)
        {
            using (var client = new HttpClient())
            {
                try
                {
                    client.BaseAddress = new Uri(currentPrivateBackendAddress);
                    
                    byte[] data;
                    using (var br = new BinaryReader(file.OpenReadStream()))
                        data = br.ReadBytes((int)file.OpenReadStream().Length);

                    ByteArrayContent bytes = new ByteArrayContent(data);

                    
                    MultipartFormDataContent multiContent = new MultipartFormDataContent();
                    
                    multiContent.Add(bytes, "file", file.FileName);

                    var result = client.PostAsync("api/Values", multiContent).Result;
                    

                    return StatusCode((int)result.StatusCode); //201 Created the request has been fulfilled, resulting in the creation of a new resource.
                                                
                }
                catch (Exception)
                {
                    return StatusCode(500); // 500 is generic server error
                }
            }
        }

        return StatusCode(400); // 400 is bad request

    }
    catch (Exception)
    {
        return StatusCode(500); // 500 is generic server error
    }
}

Private backend

[HttpPost]
public void Post()
{
    //Stream bodyStream = HttpContext.Request.Body;

    if (Request.HasFormContentType)
    {
        var form = Request.Form;
        foreach (var formFile in form.Files)
        {
            var targetDirectory = Path.Combine(_appEnvironment.WebRootPath, "uploads");

            var fileName = GetFileName(formFile);

            var savePath = Path.Combine(targetDirectory, fileName);

            using (var fileStream = new FileStream(savePath, FileMode.Create))
            {
                formFile.CopyTo(fileStream);
            }                   
        }
    }          
}

Answer 2

Hi i had the same issue and this is what worked for me :

My setup is netCore MVC netCoreApi.

My MVC Controller looks like :

[HttpPost("UploadFiles")]
public async Task<IActionResult> Post(List<IFormFile> files)
{
    Sp4RestClient dataPovider = new Sp4RestClient("http://localhost:60077/");

    long size = files.Sum(f => f.Length);

    foreach (var file in files)
    {
       await dataPovider.ImportFile(file);
    }

    return Ok();
}

DataProvider Method :

public async Task ImportFile(IFormFile file)
    {
        RestClient restClient = new RestClient(_queryBulder.BuildImportFileRequest());

        using (var content = new MultipartFormDataContent())
        {
            content.Add(new StreamContent(file.OpenReadStream())
            {
                Headers =
                {
                    ContentLength = file.Length,
                    ContentType = new MediaTypeHeaderValue(file.ContentType)
                }
            }, "File", "FileImport");

            var response = await restClient.Post<IFormFile>(content);
        }
    }

And least my WebApi Controller :

[HttpPost]
[Route("ImportData")]
public IActionResult Import(IFormFile file)
{         
    return Ok();
}

To see the complete code here is my RestClient Post method :

public async Task<RestResult<T>> Post<T>(HttpContent content)
    {
        using (HttpClient httpClient = new HttpClient())
        {
            HttpResponseMessage response = await httpClient.PostAsync(Endpoint, content);
            if (response.StatusCode == HttpStatusCode.Created)
            {
                T result = JsonConvert.DeserializeObject<T>(await response.Content.ReadAsStringAsync());
                return new RestResult<T> { Result = result, ResultCode = HttpStatusCode.OK };
            }
            RestResult<T> nonOkResult =
                new RestResult<T> { Result = default(T), ResultCode = response.StatusCode, Message = await response.Content.ReadAsStringAsync() };
            return nonOkResult;
        }
    }

// Yeah i know im not getting HttpStatusCode.Created back ;)

happy coding ;)

Answer 3

API Code

 [Route("api/upload/{id}")]
    [HttpPost]
    public async Task<IActionResult> Post(string id)
    {
        var filePath = @"D:\" + id; //+ Guid.NewGuid() + ".png";
        if (Request.HasFormContentType)
        {
            var form = Request.Form;
            foreach (var formFile in form.Files)
            {
                if (formFile.Length > 0)
                {
                    using (var stream = new FileStream(filePath, FileMode.Create))
                    {
                        await formFile.CopyToAsync(stream);
                    }
                }
            }
        }
        return Ok(new { Path = filePath });
    }

Back End

        [Route("home/UploadFile")]
    [HttpPost]
    public IActionResult UploadFile(IFormFile file)
    {
        if (file == null || file.Length == 0)
            return Content("file not selected");

        var client = new HttpClient();

        byte[] data;
        using (var br = new BinaryReader(file.OpenReadStream()))
            data = br.ReadBytes((int)file.OpenReadStream().Length);
        ByteArrayContent bytes = new ByteArrayContent(data);
        MultipartFormDataContent multiContent = new MultipartFormDataContent
        {
            { bytes, "file", file.FileName }
        };
        var result = client.PostAsync("http://localhost:2821/api/upload/" + file.FileName, multiContent).Result;
        return RedirectToAction("file");
    }

---

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