HTTP post XML data in C# (Error in request.GetRequestStream())

I need to Post the XML data to a URL.But I am facing some Error in the (Stream requestStream = request.GetRequestStream()) Line Errror Image . I have saved the xml in the file and provided the path for that . I think there is Issue while passing XML Data but when I try to use the same XML in the POSTMan using POSTmethod.I can able to get the response Data.

This is the reference link HTTP post XML data in C#

And here is my code

static void Main(string[] args)
    {
    

        string url = "*****************";
        XmlDocument Xdoc = new XmlDocument();
        Xdoc.Load(@"Path of the xml file");
        var sw = new StringWriter();
        Xdoc.Save(sw);
        string result = sw.ToString();
        string response = **********.postXMLData(url, result);
        Console.WriteLine(response);
        Console.ReadLine();
    }

public static string postXMLData(string destinationUrl, String requestXml)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(destinationUrl);
        byte[] bytes;
        bytes = System.Text.Encoding.ASCII.GetBytes(requestXml);
        request.ContentType = "text/xml; encoding=utf-8";
        request.ContentLength = bytes.Length;
        request.Method = "POST";
        using (Stream requestStream = request.GetRequestStream())
        {
            requestStream.Write(bytes, 0, bytes.Length);
        }
        HttpWebResponse response;
        response = (HttpWebResponse)request.GetResponse();
        if (response.StatusCode == HttpStatusCode.OK)
        {
            Stream responseStream = response.GetResponseStream();
            string responseStr = new StreamReader(responseStream).ReadToEnd();
            return responseStr;
        }
        return null;
    }