string szUsername = "c0relynx";
string szPassword = "c0relynx";
string szURL1 ="http://xx.xx.xx.xx/webdav/foobar1.txt";
string szContent = String.Format(@"Date/Time: {0} {1}", DateTime.Now.ToShortDateString(), DateTime.Now.ToLongTimeString());

HttpWebRequest httpPutRequest = (HttpWebRequest)WebRequest.Create(szURL1);

httpPutRequest.Credentials = new NetworkCredential(szUsername, szPassword);

httpPutRequest.PreAuthenticate = true;

httpPutRequest.Method = @"PUT";

httpPutRequest.Headers.Add(@"Overwrite", @"T");

httpPutRequest.ContentLength = szContent.Length;

httpPutRequest.SendChunked = true;

httpPutRequest.KeepAlive = true;

Stream requestStream = httpPutRequest.GetRequestStream();

requestStream.Write(Encoding.UTF8.GetBytes((string)szContent), 0, szContent.Length);

requestStream.Close();
HttpWebResponse httpPutResponse = (HttpWebResponse)httpPutRequest.GetResponse();