执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出

HttpWebResponse httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse

不是代码的问题，而是你这个请求的URL是否有效

用

if(httpWebResponse.StatusCode == HttpStatusCode.OK)

{

//请求正确

}

else

{

//请求错误，关闭会话

}

HttpWebRequest req = (HttpWebRequest)WebRequest.Create(URL)

req.Timeout = 15000//超时时间

req.CookieContainer = new CookieContainer()

req.UserAgent = "Mozilla/4.0 (compatibleMSIE 7.0Windows NT 5.2.NET CLR 1.1.4322.NET CLR 2.0.50727)"

req.ContentType = "multipart/form-data"

WebResponse resp = req.GetResponse()

StreamReader sr = new StreamReader(resp.GetResponseStream(), Encoding.UTF8)

sReturn = sr.ReadToEnd().Trim()

resp.Close()

sr.Close()

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