Asp. NET background Invoke API method

<summary>
Call API Post request and get results
</summary>

URL and JSON string
public static string HttpPost (String Url, String postdatastr)
{
HttpWebRequest request = (HttpWebRequest) webrequest.create (URL);
Request. Method = "POST";
Request. ContentType = "Application/json";
Request. ContentLength = Postdatastr.length;
StreamWriter writer = new StreamWriter (Request. GetRequestStream (), Encoding.UTF8);
Writer. Write (POSTDATASTR);
Writer. Flush ();
HttpWebResponse response = (HttpWebResponse) request. GetResponse ();
String encoding = Response. ContentEncoding;
if (encoding = = NULL | | encoding. Length < 1)
{
encoding = "UTF-8"; Default encoding
}
StreamReader reader = new StreamReader (response. GetResponseStream (), encoding.getencoding (Encoding));
String retstring = reader. ReadToEnd ();

return retstring;
}

Asp. NET background Invoke API method