HttpWebRequest 请求带OAuth2 授权的webapi

OAuth 2.0注意事项：
1、 获取access_token时，请使用POST

  private static string GetAuthorization(string username, string password)

         {

             string authorization = string.Format("{0}:{1}", username, password);

             return "Basic " + Convert.ToBase64String(new ASCIIEncoding().GetBytes(authorization));

         }

   /// <summary>

         /// 获取Token

         /// </summary>

         /// <returns></returns>

         private static string OAuthClientCredentialsToken()

         {

             const string clientId = "";

             const string clientSecret = "";

             string result = string.Empty;

             HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(_baseUrl + "/token");

             httpWebRequest.Method = "POST";

             httpWebRequest.ContentType = "application/x-www-form-urlencoded";

             httpWebRequest.Accept = "application/json";

             httpWebRequest.Timeout = ;

             httpWebRequest.KeepAlive = false;

             httpWebRequest.AllowAutoRedirect = true;

             // httpWebRequest.Headers.Add("Accept-Language", "zh-cn");

             //  httpWebRequest.Headers.Add("Accept-Encoding", "gzip, deflate");

             // httpWebRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.1.4322)";

             httpWebRequest.Headers.Add("Authorization", GetAuthorization(clientId, clientSecret));

             //Credentials

             httpWebRequest.Credentials = CredentialCache.DefaultCredentials;

             //post参数

             StringBuilder postParam = new StringBuilder();

             Dictionary<string, string> parameters = new Dictionary<string, string> { { "grant_type", "client_credentials" } };

             int i = ;

             foreach (KeyValuePair<string, string> parameter in parameters)

             {

                 if (i > )

                     postParam.Append("&");

                 postParam.AppendFormat("{0}={1}", parameter.Key, HttpUtility.UrlEncode(parameter.Value));

                 i++;

             }

             byte[] postData = Encoding.UTF8.GetBytes(postParam.ToString());

             httpWebRequest.ContentLength = postData.Length;

             try

             {

                 Stream requesStream = httpWebRequest.GetRequestStream();

                 requesStream.Write(postData, , postData.Length);

                 requesStream.Close();

                 WebResponse response = httpWebRequest.GetResponse();

                 Stream stream = response.GetResponseStream();

                 if (stream != null)

                 {

                     using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))

                     {

                         result = reader.ReadToEnd();

                         reader.Close();

                     }

                     stream.Close();

                 }

             }

             catch (WebException ex)

             {

                 throw new Exception(ex.Message);

             }

             return !string.IsNullOrWhiteSpace(result) ? JObject.Parse(result)["access_token"].Value<string>() : result;

         }

2、 访问需要授权的Api，请使用http/https协议，并且加上access token的Header
3 、Header格式为"Authorization: Bearer access_token"，其中Bearer后面有一个空格

  /// <summary>

         /// HttpGet

         /// </summary>

         /// <param name="url"></param>

         /// <param name="token"></param>

         /// <param name="contentType"></param>

         /// <returns></returns>

         private static string HttpGet(string url, string token, string contentType = "application/x-www-form-urlencoded")

         {

             HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

             httpWebRequest.Method = "GET";

             httpWebRequest.ContentType = contentType;

             httpWebRequest.Accept = "application/json";

             httpWebRequest.Timeout = ;

             httpWebRequest.AllowAutoRedirect = false;

             //Bearer+空格

             httpWebRequest.Headers.Add("Authorization", "Bearer " + token);

             httpWebRequest.Credentials = CredentialCache.DefaultCredentials;

             string result = null;

             try

             {

                 WebResponse response = httpWebRequest.GetResponse();

                 Stream responseStream = response.GetResponseStream();

                 if (responseStream != null)

                 {

                     using (StreamReader streamReader = new StreamReader(responseStream, Encoding.UTF8))

                     {

                         result = streamReader.ReadToEnd();

                         streamReader.Close();

                     }

                 }

             }

             catch (Exception ex)

             {

                 throw new Exception(ex.Message);

             }

             return result;

         }