Update .gitlab-ci.yml file in GitLab using Gitlab API in C# - asp.net-core

Question

I am working on a project that has a file .gitlab-ci.yml in master branch. I am trying to update that .yml file using gitlab api (https://docs.gitlab.com/ee/api/commits.html#create-a-commit-with-multiple-files-and-actions) but using it from a asp.net core 5 application.
Here is my try. But I am getting 400 bad request error. Kindly help to find out what is wrong I am doing here.
public IActionResult Update()
{
var url = $"{ProjectUrl}/{ProjectId}/repository/commits/";
var httpRequest = (HttpWebRequest)WebRequest.Create(url);
httpRequest.Method = "PUT";
httpRequest.Headers["PRIVATE-TOKEN"] = ClientSecret;
httpRequest.ContentType = "application/json";
var str =
#"{'branch': 'master',
'commit_message': 'some commit message',
'actions': [
{
'action': 'update',
'file_path': '.gitlab-ci.yml',
'content': 'some content'
}
}";
var data = str;
using (var streamWriter = new StreamWriter(httpRequest.GetRequestStream()))
{
streamWriter.Write(data);
}
var httpResponse = (HttpWebResponse)httpRequest.GetResponse(); // I'm getting 400 Bad request error here
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
var result = streamReader.ReadToEnd();
// rest of the code goes here
}
return View();
}

Answer 1

Well after rewriting the code, finally I am able to make it works. Posting my solution here in a hope that someone will be benefited from this. Cheers!
using (var httpClient = new HttpClient())
{
using (var request = new HttpRequestMessage(new HttpMethod("PUT"), "https://ProjectUrl/api/v4/projects/projectid/repository/%2Egitlab%2Dci.yml"))
{
request.Headers.TryAddWithoutValidation("PRIVATE-TOKEN", "<your_private_token>");
request.Content = new StringContent("{\"branch\": \"master\", \"author_email\": \"user#email.com\", \"author_name\": \"user\", \n \"content\": \"some content\", \"commit_message\": \"update file\"}");
request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
var response = await httpClient.SendAsync(request);
}
}