.NET WebApi - How to receive a file with additional parameters?

Question

Noob question here, i'm trying to send a file with one added string parameter. My uploader class looks like that:

 public static void HttpUploadFile(string url, string file, string paramName, string contentType, NameValueCollection nvc)
        {
            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

            HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);
            wr.ContentType = "multipart/form-data; boundary=" + boundary;
            wr.Method = "POST";
            wr.KeepAlive = true;
            wr.Credentials = System.Net.CredentialCache.DefaultCredentials;
            Stream rs = wr.GetRequestStream();
            string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
            foreach (string key in nvc.Keys)
            {
                rs.Write(boundarybytes, 0, boundarybytes.Length);
                string formitem = string.Format(formdataTemplate, key, nvc[key]);
                byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
                rs.Write(formitembytes, 0, formitembytes.Length);
            }
            rs.Write(boundarybytes, 0, boundarybytes.Length);
            string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
            string header = string.Format(headerTemplate, paramName, file, contentType);
            byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
            rs.Write(headerbytes, 0, headerbytes.Length);
            FileStream fileStream = new FileStream(file, FileMode.Open, FileAccess.Read);
            byte[] buffer = new byte[4096];
            int bytesRead = 0;
            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
            {
                rs.Write(buffer, 0, bytesRead);
            }
            fileStream.Close();
            byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
            rs.Write(trailer, 0, trailer.Length);
            rs.Close();
            WebResponse wresp = null;
            try
            {
                wresp = wr.GetResponse();
                Stream stream2 = wresp.GetResponseStream();
                StreamReader reader2 = new StreamReader(stream2);
               var result = reader2.ReadToEnd();
            }
            catch (Exception ex)
            {
                Program.log.Error(System.Reflection.MethodBase.GetCurrentMethod().Name + " Error occurred while converting file ", ex);
                if (wresp != null)
                {
                    wresp.Close();
                    wresp = null;
                }
            }
            finally
            {
                wr = null;
            }
        }

The string parameters are inside the NameValueCollection. Now how should the other side, the post method, receive it?

*Also, in this cases where i mix a file + string parameters, should the content type be "application/octet-stream"?

Thanks

Answer 1

For your case, you can create a FileUploadViewModel to contain all your properties including IFormFile. Use this as parameter type to your action method. Default model binder should be able to populate everything for you.

Also see if you need a custom model binder - https://learn.microsoft.com/en-us/aspnet/core/mvc/advanced/custom-model-binding?view=aspnetcore-2.1