How to split an HTTP Request Body in two parts?

I'm fairly new to use HTTPClient and sending REST requests to APIs, I'm currently practicing multipart upload using this Google Drive API endpoint: POST https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart There's an instruction that states there to split the request body into two parts, I tried to recreate this but was unable to do so. https://developers.google.com/drive/api/guides/manage-uploads#multipart Here's my current code:

async void UploadFile(StorageFile fileName) < using (HttpClient client = new HttpClient()) < // Opens files and convert it to stream var resultStream = await fileName.OpenReadAsync(); var fileStreamContent = new StreamContent(resultStream.AsStream()); // Create file MetaData var fileMetaData = JsonConvert.SerializeObject( new < name = fileName.Name, mimetype = fileName.ContentType >); // Create POST request var requestMessage = new HttpRequestMessage(HttpMethod.Post, uploadFileEndpoint); requestMessage.Headers.Authorization = new AuthenticationHeaderValue(tokenType, accessToken); // Add request body requestMessage.Content = new StringContent(fileMetaData, Encoding.UTF8, "application/json"); requestMessage.Content.Headers.ContentType = new MediaTypeHeaderValue("multipart/related"); var response = await client.SendAsync(requestMessage); string responseString = await response.Content.ReadAsStringAsync(); output(responseString); > >
Any help would be greatly appreciated, thank you! 48.6k 5 5 gold badges 32 32 silver badges 56 56 bronze badges asked Jan 13, 2023 at 3:01 Martin King Martin King 47 1 1 silver badge 7 7 bronze badges Don't use StringContent , you probably want learn.microsoft.com/en-us/dotnet/api/… Commented Jan 13, 2023 at 3:04 @JeremyLakeman Hi, can you provide an example? Thank you Commented Jan 13, 2023 at 3:06

1 Answer 1

According to the documentation on Perform a multipart upload (HTTP tab), you need the MultipartFormDataContent as suggested by @Jeremy.

There are a few things needed to perform/migrate:

  1. Add AuthenticationHeaderValue into client.DefaultRequestHeaders.Authorization .
  2. Create a StreamContent instance, fileStreamContent (which you have done) and specify its Headers.ContentType .
  3. Create a StringContent instance, stringContent (which you have done).
  4. Append both StreamContent and StringContent into the MultipartFormDataContent instance, formData .
  5. Specify the formData 's Headers.ContentType as requested in API docs.
  6. Post the formData with await client.PostAsync(/* API Url */, formData);
using (HttpClient client = new HttpClient()) < client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(tokenType, accessToken); // Opens files and convert it to stream var resultStream = await fileName.OpenReadAsync(); var fileStreamContent = new StreamContent(resultStream.AsStream()); fileStreamContent.Headers.ContentType = new MediaTypeHeaderValue(fileName.ContentType); // Create file MetaData var fileMetaData = JsonConvert.SerializeObject(new < name = fileName.Name, mimetype = fileName.ContentType >); var stringContent = new StringContent(fileMetaData, Encoding.UTF8, "application/json"); // Create POST request MultipartFormDataContent formData = new MultipartFormDataContent(); formData.Add(stringContent, "metadata"); formData.Add(fileStreamContent, "media"); formData.Headers.ContentType = new MediaTypeHeaderValue("multipart/related"); var response = await client.PostAsync(uploadFileEndpoint, formData); string responseString = await response.Content.ReadAsStringAsync(); >