这是我今天下午碰到的案例，一个退订页面的post请求，请求头信息都很明确，but看看下面这个请求体，除了最后一个key是我的页面控件名称，其他的几个ViewState相关都是what呢？（ViewState原理参考http://www.cnblogs.com/wwan/archive/2010/11/18/1880357.html），下面是怎么处理这种情况的Post请求的办法。
1. 拿到接口地址，参数，拼串发送Get请求，拿到响应体(如下图，看高亮)
2. 从响应体里提取我们想要的ViewState相关，并保持在相应的字符串里面
3. 拼出来我们想要的请求体，对刚才的地址重新发送Post请求
亲测，可以解决问题。
请求头 Content-Type：Content-Type: application/x-www-form-urlencoded
public static string unsubResponse(string UnsubURL)
{
try
{
// Get the ViewState and EventValidation
HttpWebRequest request = WebRequest.Create(UnsubURL) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = false; // Get the response
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
Stream responseStream = response.GetResponseStream();
StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
string srcString = reader.ReadToEnd(); //Get the __VIEWSTATE
string viewStateFlag = "id=\"__VIEWSTATE\" value=\"";
int i = srcString.IndexOf(viewStateFlag) + viewStateFlag.Length;
int j = srcString.IndexOf("\"", i);
string viewState = srcString.Substring(i, j - i); // Get the __VIEWSTATEGENERATOR
string viewStateGeneratorFlag = "id=\"__VIEWSTATEGENERATOR\" value=\"";
i = srcString.IndexOf(viewStateGeneratorFlag) + viewStateGeneratorFlag.Length;
j = srcString.IndexOf("\"", i);
string viewStateGenerator = srcString.Substring(i, j - i); // Get the __EVENTVALIDATION
string EventValidationFlag = "id=\"__EVENTVALIDATION\" value=\"";
i = srcString.IndexOf(EventValidationFlag) + EventValidationFlag.Length;
j = srcString.IndexOf("\"", i);
string eventValidation = srcString.Substring(i, j - i); // Compose the URL
viewState = Uri.EscapeDataString(viewState);
viewStateGenerator = Uri.EscapeDataString(viewStateGenerator);
eventValidation = Uri.EscapeDataString(eventValidation);
string unsubButton = Uri.EscapeDataString("Unsubscribe"); string formatString = "__VIEWSTATE={0}&__VIEWSTATEGENERATOR={1}&__EVENTVALIDATION={2}&ButtonUnsubscribe={3}";
string postString = string.Format(formatString, viewState, viewStateGenerator, eventValidation, unsubButton); // Change to byte[]
byte[] postData = Encoding.ASCII.GetBytes(postString); // Compose the new request
request = WebRequest.Create(UnsubURL) as HttpWebRequest;
request.Method = "POST";
request.KeepAlive = false;
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = postData.Length; Stream outputStream = request.GetRequestStream();
outputStream.Write(postData, , postData.Length);
outputStream.Close(); // Get the new response
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new StreamReader(responseStream);
srcString = reader.ReadToEnd();
return (srcString);
}
catch (WebException we)
{
Console.WriteLine("Communication error," + we.Message + " please check your connectivity and try again.", "Error");
}
catch
{
Console.WriteLine("Unknow error.", "Error");
}
return (null);
}