C# 類比post資料提交時 出現如下錯誤: System.Net.WebException: 遠程伺服器返回錯誤: (417) Expectation Failed 的解決辦法

一般情況的代碼，重點在出錯的那段代碼，其他的代碼可以根據自己的情況寫相應的代碼：

HttpWebRequest req=WebRequest.Create(url1) as HttpWebRequest;
   req.Method="POST";
   req.Accept="application/json, text/javascript, */*";
   req.Referer=url2;

   req.UserAgent="Mozilla/4.0";
   req.ContentType="application/x-www-form-urlencoded";
   req.CookieContainer=cookie;
   req.KeepAlive=true;
   string postString="uname=ioriliaotest3&" +
                  "password=19850420&" +
                  "passwordconf=19850420" +
                  "&mobile=&verifycode="+
                   HttpUtility.UrlEncode(textBox1.Text,encoding)+
                  "&dmain=163.com&version=regvf1";
   byte[] postByte=Encoding.ASCII.GetBytes(postString);
   Stream reqStream=req.GetRequestStream();
   reqStream.Write(postByte,0,postByte.Length);
   reqStream.Close();
   HttpWebResponse resp=req.GetResponse() as HttpWebResponse;//出錯 WebException: 遠程伺服器返回錯誤: (417) Expectation Failed
   Stream respStream=resp.GetResponseStream();
   StreamReader respReader=new StreamReader(respStream,encoding);
   richTextBox1.AppendText(respReader.ReadToEnd());
   respStream.Close();
   respReader.Close();

歸納其原因：
httpwebrequest控制項有一個透明過程，先向服務方查詢url是否存在而不發送POST的內容，伺服器如果證實url是可訪問的，才發送POST，早期的Apache就認為這是一種錯誤，而IIS卻可以正確應答

解決方案：

寫.net程式時在始化代碼中，或者設定檔app.config之類的檔案中
加下這麼一句就可以了

ServicePointManager.Expect100Continue = false;