How to make a web service request to upload .csv file? Converting curl to c#

Hello,

API Document: https://api.qualtrics.com/reference#start-import

Here is the curl code:

curl-X POST -H'X-API-TOKEN: yourapitoken' \-H'Content-Type: text/csv; charset=UTF-8' \--data-binary'@example.csv' \'https://yourdatacenterid.qualtrics.com/API/v3/surveys/SV_123456/import-responses'

The below codes runs without any error but status is failed when I check progress status of the file upload.

ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://yourdatacenterid.qualtrics.com/API/v3/surveys/surveyid/import-responses");
request.Method = "POST";
request.ContentType = "text/csv; charset=UTF-8";
request.Headers.Add("X-API-TOKEN", "xxxxxxxxxxx");

//ByteArrayContent bytes = new ByteArrayContent(File.ReadAllBytes(@"H:\Qualtrics Project Management\API Import Testing\RealSurveyProject_API_Import.csv"));
Stream requestStream = request.GetRequestStream();
//using (var streamWriter = new Stream(request.GetRequestStream()))
//{
using (FileStream fileStream = new FileStream(@"H:\Qualtrics Project Management\API Import Testing\RealSurveyProject_API_Import.csv", FileMode.Open, FileAccess.Read))
{
byte[] buffer = new byte[1024];
int bytesRead = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
requestStream.Write(buffer, 0, bytesRead);
}
fileStream.Close();
}
//streamWriter.Write(bytes);
//streamWriter.Flush();
requestStream.Close();

var httpResponse = (HttpWebResponse)request.GetResponse();

using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
var result = streamReader.ReadToEnd();
Console.WriteLine(result.ToString());
}
//}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message.ToString());
}