HttpWebRequest请求返回非200的时候 HttpWebResponse怎么接受返回错误提示

当我们使用HttpWebRequest发送请求的时候如果服务器返回的不是200状态，那么请求代码肯定会异常，其实请求和返回并没有什么异常，只是.net内部就认定了 返回的不要是200 就是异常

那么我们怎么捕获这个HttpWebResponse异常呢

try
{
HttpWebRequest httpReq = WebRequest.Create(Url) as HttpWebRequest;
WebResponse wenReq = null;
HttpWebResponse httpRes = null;
string OutHtml = "";

try
{
httpReq.Method = "POST";
//.................
//写入参数
byte[] postData = Encoding.UTF8.GetBytes(parmst);//参数编码UTF-8
System.IO.Stream outputStream = httpReq.GetRequestStream();
outputStream.Write(postData, 0, postData.Length);
outputStream.Close();
//这里如果服务器不返回200状态就会报异常
wenReq = httpReq.GetResponse();
httpRes = wenReq as HttpWebResponse;
Stream strRes = httpRes.GetResponseStream();
using (StreamReader read = new StreamReader(strRes, Encoding.UTF8))
{
OutHtml = read.ReadToEnd();
}
httpReq.Abort();
strRes.Close();
strRes.Dispose();
httpRes.Close();
}
catch (WebException ex) // 这样我们就能捕获到异常，并且获取服务器端的输出
{
wenReq = (HttpWebResponse)ex.Response;
using (StreamReader sr = new StreamReader(wenReq.GetResponseStream(), Encoding.UTF8))
{
LogResult(Url + ";Exception Err:" + ex.Message + ";Err JSON:" + sr.ReadToEnd(), "httperr");
}
httpReq.Abort();
}
catch (Exception ex)
{
//bgTask g = new bgTask();
LogResult(Url + ";Exception Err:" + ex.Message, "httperr");
}