The remote server returned an error: (417) Expectation failed

今天利用twitter的search api做个搜索，做了个小demo。新建了个项目，直接在test页面的Page_Load里面写下了如下测试代码。

　　　　 protected void Page_Load(object sender, EventArgs e)
        {
            string urlPost = "http://search.twitter.com/search.json";

            string postData = "q=twitterapi";
            UTF8Encoding encoding = new UTF8Encoding();
            byte[] byteData = encoding.GetBytes(postData);

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlPost);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = byteData.Length;

            Stream requestStream = request.GetRequestStream();
            requestStream.Write(byteData, 0, byteData.Length);
            requestStream.Close();

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                        
            Stream receiveStream = response.GetResponseStream();

            StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8);

            Response.Write("Response stream received.");
            Response.Write(readStream.ReadToEnd());
            response.Close();
            readStream.Close();
        }

可惜出现了“The remote server returned an error: (417) Expectation failed”的错误。

开始以为是“长城防火墙”的关系，可是连上vpn后还是一样，于是去网上找解决办法，终于然我找到了原因所在。

“该错误可能是客户端网络环境引起的(don't support "100 continue" expectation)，在程序的配置文件中加上下面部分试试。” 原文地址：http://0e2.net/post/1184.html

<configuration>
  <system.net>
    <settings>
      <servicePointManager expect100Continue="false" />
    </settings>
  </system.net>
</configuration>

测试，成功！！