Adding headers with C# WebRequest post

Question

i have a post url.I need to add header parameters. But I couldn't add it, I don't know how to write the code exactly. The code I wrote is as follows

var request = WebRequest.Create(url);
request.Method = "POST";
request.Headers.Add("username", "abcd");
request.Headers.Add("password", "12345678");
request.Headers.Add("baslangicDt", "2023-01-01");
request.Headers.Add("bitisDt", "2023-05-01");
request.Headers.Add("period", "15");
request.Headers.Add("sayaceiclist","eic:40Z000000306875Z");
           
var webResponse = request.GetResponse();
var webStream = webResponse.GetResponseStream();
var reader = new StreamReader(webStream);
var data = reader.ReadToEnd();
Console.WriteLine(data);
Console.ReadLine();

Resimde örnek request parametrelerini görebilirsiniz.

Screenshot

How to post with webrequest.