C# 模拟post数据提交时 出现如下错误: System.Net.WebException: 远程服务器返回错误: (417) Expectation Failed 的解决办法

一般情况的代码，重点在出错的那段代码，其他的代码可以根据自己的情况写相应的代码：

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;//出错 WebException: 远程服务器返回错误: (417) Expectation Failed
   Stream respStream=resp.GetResponseStream();
   StreamReader respReader=new StreamReader(respStream,encoding);
   richTextBox1.AppendText(respReader.ReadToEnd());
   respStream.Close();
   respReader.Close();

归纳其原因：
httpwebrequest控件有一个透明过程，先向服务方查询url是否存在而不发送POST的内容，服务器如果证实url是可访问的，才发送POST，早期的Apache就认为这是一种错误，而IIS却可以正确应答

解决方法：

写.net程序时在始化代码中，或者配置文件app.config之类的文件中
加下这么一句就可以了

ServicePointManager.Expect100Continue  =   false ;