远程服务器返回错误:(400)错误的请求，微软的翻译接口
最近在用微软的翻译接口，但也是报 远程服务器返回错误:(400)错误的请求， 问题出在下面我标示为红色的代码，请高手指点一下错在哪了
static void Main(string[] args)
  {
  AdmAccessToken admToken;
  string headerValue;
  //Get Client Id and Client Secret from https://datamarket.azure.com/developer/applications/
  //Refer obtaining AccessToken (http://msdn.microsoft.com/en-us/library/hh454950.aspx)  
  string clientID = "hongxuebiaoTranslator";
  string clientSecret = "KJn2ZfUPAAruDJECbpg7MrzsNWGiHtcmjmeQJYkD6hw";
  AdmAuthentication admAuth = new AdmAuthentication(clientID, clientSecret);
  try
  {
  admToken = admAuth.GetAccessToken();
  // Create a header with the access_token property of the returned token
  headerValue = "Bearer " + admToken.access_token;
  TranslateMethod(headerValue);
  }
  catch (WebException e)
  {
  ProcessWebException(e);
  Console.WriteLine("Press any key to continue...");
  Console.ReadKey(true);
  }
  catch (Exception ex)
  {

  Console.WriteLine(ex.Message);
  Console.WriteLine("Press any key to continue...");
  Console.ReadKey(true);
  }
  }
  private static void TranslateMethod(string authToken)
  {

  string text = "Use pixels to express measurements for padding and margins.";
  string from = "en";
  string to = "de";

  string uri = "http://api.microsofttranslator.com/v2/Http.svc/Translate?text=" + System.Web.HttpUtility.UrlEncode(text) + "&from=" + from + "&to=" + to;

  HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(uri);
  httpWebRequest.Headers.Add("Authorization", authToken);
  WebResponse response = null;
  try
  {
  response = httpWebRequest.GetResponse();
  using (Stream stream = response.GetResponseStream())
  {
  System.Runtime.Serialization.DataContractSerializer dcs = new System.Runtime.Serialization.DataContractSerializer(Type.GetType("System.String"));
  string translation = (string)dcs.ReadObject(stream);
  Console.WriteLine("Translation for source text '{0}' from {1} to {2} is", text, "en", "de");
  Console.WriteLine(translation);

  }
  Console.WriteLine("Press any key to continue...");
  Console.ReadKey(true);
  }
  catch
  {
  throw;
  }
  finally
  {
  if (response != null)
  {
  response.Close();
  response = null;
  }
  }
  }
  private static void ProcessWebException(WebException e)
  {
  Console.WriteLine("{0}", e.ToString());
  // Obtain detailed error information
  string strResponse = string.Empty;
  using (HttpWebResponse response = (HttpWebResponse)e.Response)
  {
  using (Stream responseStream = response.GetResponseStream())
  {
  using (StreamReader sr = new StreamReader(responseStream, System.Text.Encoding.ASCII))
  {
  strResponse = sr.ReadToEnd();
  }
  }
  }
  Console.WriteLine("Http status code={0}, error message={1}", e.Status, strResponse);
  }
  }
  [DataContract]
  public class AdmAccessToken
  {
  [DataMember]