Bytes to be written to the stream exceed the Content-Length bytes size specified

Question

I have a Web API which uploads the File content to the server.

[HttpPost]
[Route("SaveFileContent")]
public async Task<FileResponse> SaveFileContent([FromForm] SaveFileContentRequest request)
{
   return await _service.SaveFile(request);
}

This is my call to the API:

public async Task<FileResponse> SaveFileContent(SaveFileContentRequest request)
{
   try
   {
        var uri = "https://www.mycompanyurl.com";
    
        using (var client = new HttpClient())
        {
            using (var form = new MultipartFormDataContent())
            {
                 using (var fileContent = new ByteArrayContent(request.File))
                 {
                     fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");

                     form.Add(fileContent, "file", request.FileName);
                     form.Add(new StringContent(request.MemberId), "MemberId");
                     form.Add(new StringContent(request.Country), "Country");

                     client.BaseAddress = new Uri(uri);
                     HttpResponseMessage response = await client.PostAsync("/api/Document/SaveFileContent", form);
                     FileResponse result = JsonConvert.DeserializeObject<FileResponse>(response.Content.ReadAsStringAsync().Result);
                     return result;
                }
            }
        }
      }
 
    catch (Exception ex)
    {
        ex.LogError(ex);
    }
    }

With this, the call is successfully made to the API and the file is saved on the server.

But, when I added 2 new StringContent to the MultipartFormDataContent:

  form.Add(new StringContent(request.Source), "Source");
  form.Add(new StringContent(request.UserName), "UserName");

I am getting this exception:

Bytes to be written to the stream exceed the Content-Length bytes size specified

How do I resolve this?