gistfile1.cs

var request = (HttpWebRequest) HttpWebRequest.Create("https://example.com/foo");
request.ServicePoint.Expect100Continue = false;
request.Credentials = new NetworkCredential("user", "password");
request.Method = "PUT";
request.ContentType = "application/x-www-form-urlencoded";
byte[] objByteArray = Encoding.UTF8.GetBytes("foo=bar");
request.ContentLength = objByteArray.Length;
var dataStream = request.GetRequestStream();
dataStream.Write(objByteArray, 0, objByteArray.Length);
dataStream.Close();

var response = request.GetResponse();