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;