调用新浪微博api发微博出现的问题

Question

//准备用户验证数据：
  string username = "";//博客帐号
  string password = "";//密码
  string appkey="";//申请的app key
  string usernamePassword = username + ":" + password;
  //准备调用的URL及需要POST的数据：
  string url = "http://api.t.sina.com.cn/statuses/update.xml";
  string news_title = "api测试";
  string t_news = string.Format("{0}，http://www.XXXXX.com", news_title);
  string data = "source="+appkey+"&status=" + System.Web.HttpUtility.UrlEncode(t_news);
  //准备用于发起请求的HttpWebRequest对象：
  System.Net.WebRequest webRequest = System.Net.WebRequest.Create(url);
  System.Net.HttpWebRequest httpRequest = webRequest as System.Net.HttpWebRequest;
  //准备用于用户验证的凭据： 
  System.Net.CredentialCache myCache = new System.Net.CredentialCache();
  myCache.Add(new Uri(url), "Basic", new System.Net.NetworkCredential(username, password));
  httpRequest.Credentials = myCache;
  httpRequest.Headers.Add("Authorization", "Basic " +
  Convert.ToBase64String(new System.Text.ASCIIEncoding().GetBytes(usernamePassword)));
  //发起POST请求：
  httpRequest.Method = "POST";
  httpRequest.ContentType = "application/x-www-form-urlencoded";
  System.Text.Encoding encoding = System.Text.Encoding.ASCII;
  byte[] bytesToPost = encoding.GetBytes(data);
  httpRequest.ContentLength = bytesToPost.Length;
  System.IO.Stream requestStream = httpRequest.GetRequestStream();
  requestStream.Write(bytesToPost, 0, bytesToPost.Length);
  requestStream.Close();

  System.Net.WebResponse wr = httpRequest.GetResponse();
  System.IO.Stream receiveStream = wr.GetResponseStream();
  using (System.IO.StreamReader reader = new System.IO.StreamReader(receiveStream, System.Text.Encoding.UTF8))
  {
  this.TextBox2.Text = reader.ReadToEnd();
  }
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运行到 System.Net.WebResponse wr = httpRequest.GetResponse();时出错错误
远程服务器返回错误: (400) 错误的请求。 
求高手解惑~~！！！！万分感谢

Answer 1

没有人帮忙看下么？

Answer 2

你好，

你单步debug下，看看哪个地方出问题的。

Answer 3

估计是授权问题