How to upload a file and a parameter to a remote server via HttpClient PostAsync method?

Question

I'm attempting to upload a file from my desktop application to a remote server. After browsing SO for a while this approach seems to be the cleanest way to go about it. The problem is neither parameter is received at the server side. What am I missing?

    private void AddFile(FileInfo fileInfo, int folderId)
    {
        using (var handler = new HttpClientHandler() {CookieContainer = _cookies})
        {
            using (var client = new HttpClient(handler) {BaseAddress = new Uri(_host)})
            {
                var requestContent = new MultipartFormDataContent();
                var fileContent = new StreamContent(fileInfo.Open(FileMode.Open));
                var folderContent = new StringContent(folderId.ToString(CultureInfo.InvariantCulture));
                requestContent.Add(fileContent, "file", "file");
                requestContent.Add(folderContent, "folderId", "folderId");

                client.PostAsync("/Company/AddFile", requestContent);
            }
        }
    }

edit: This is the signature the server side is expecting:

    [HttpPost]
    public ActionResult AddFile(HttpPostedFileBase file, int folderId)

Answer 1

After a lot of trial and error I got it. There were a few problems. 1) paramater names are expected in quotes 2) I was missing a bunch of header information. Here's the working code.

    private void AddFile(FileInfo fileInfo, int folderId)
    {
        using (var handler = new HttpClientHandler() {CookieContainer = _cookies})
        {
            using (var client = new HttpClient(handler) {BaseAddress = new Uri(_host)})
            {
                var requestContent = new MultipartFormDataContent();
                var fileContent = new StreamContent(fileInfo.OpenRead());
                fileContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
                    {
                        Name = "\"file\"",
                        FileName = "\"" + fileInfo.Name + "\""
                    };
                fileContent.Headers.ContentType =
                    MediaTypeHeaderValue.Parse(MimeMapping.GetMimeMapping(fileInfo.Name));
                var folderContent = new StringContent(folderId.ToString(CultureInfo.InvariantCulture));

                requestContent.Add(fileContent);
                requestContent.Add(folderContent, "\"folderId\"");

                var result = client.PostAsync("Company/AddFile", requestContent).Result;
            }
        }

Answer 2

At client end: using (var formData = new MultipartFormDataContent()) { formData.Add(new StreamContent(new MemoryStream(bytes)), "file", Model.BaseFileName); string result = client.PostAsync(" https://fakeurl.com/Controller/Action?inputParams= " + Params, formData).Result.Content.ReadAsStringAsync().Result;}

At Server End: var httpRequest = System.Web.HttpContext.Current.Request;

            if (httpRequest.Files.Count > 0)
            {
                var docfiles = new List<string>();
                //foreach (string file in httpRequest.Files)
                //{
                HttpPostedFile postedFile = httpRequest.Files[0];
                // Initialize the stream.
                Stream mstream = postedFile.InputStream;

                byte[] byteArray = new byte[postedFile.ContentLength];
                postedFile.InputStream.Read(byteArray, 0, postedFile.ContentLength);

Answer 3

This article propose a complete solution:https://makolyte.com/csharp-how-to-send-a-file-with-httpclient/

Code to upload a single file:

var filePath = @"C:\house.png";

using (var multipartFormContent = new MultipartFormDataContent())
{
    //Load the file and set the file's Content-Type header
    var fileStreamContent = new StreamContent(File.OpenRead(filePath));
    fileStreamContent.Headers.ContentType = new MediaTypeHeaderValue("image/png");

    //Add the file
    multipartFormContent.Add(fileStreamContent, name: "file", fileName: "house.png");

    //Send it
    var response = await httpClient.PostAsync("https://localhost:12345/files/", multipartFormContent);
    response.EnsureSuccessStatusCode();
    return await response.Content.ReadAsStringAsync();
}

Code to upload a file and some form fields:

var filePath = @"C:\house.png";

using (var multipartFormContent = new MultipartFormDataContent())
{
    //Add other fields
    multipartFormContent.Add(new StringContent("123"), name: "UserId");
    multipartFormContent.Add(new StringContent("Home insurance"), name: "Title");

    //Add the file
    var fileStreamContent = new StreamContent(File.OpenRead(filePath));
    fileStreamContent.Headers.ContentType = new MediaTypeHeaderValue("image/png");
    multipartFormContent.Add(fileStreamContent, name: "file", fileName: "house.png");

    //Send it
    var response = await httpClient.PostAsync("https://localhost:12345/files/", multipartFormContent);
    response.EnsureSuccessStatusCode();
    return await response.Content.ReadAsStringAsync();
}