ASP.Net | POST request in C# with content-type being x-www-form-urlencoded

The following code makes a POST request in C# with content-type being x-www-form-urlencoded:

HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.Method = "POST";
webRequest.AllowAutoRedirect = true;
webRequest.Timeout = 20 * 1000;
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
webRequest.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36";

//write the data to post request
//Postdata : a=1&b=2&c=3
byte[] buffer = Encoding.Default.GetBytes(Postdata);
if (buffer != null)
{
     webRequest.ContentLength = buffer.Length;
     webRequest.GetRequestStream().Write(buffer, 0, buffer.Length);
}

HttpWebResponse response = (HttpWebResponse)webRequest.GetResponse();
Stream dataStream = response.GetResponseStream();
StreamReader reader = new StreamReader(dataStream);
string strResponse = reader.ReadToEnd();