HttpWebRequest 返回BadRequest(400)

问题背景：

使用 HttpWebRequest 调用 GetResponse() 方法，返回 WebException，HttpStatusCode 是 400，无法获取返回的错误信息；

解决方式：

在 catch 中捕获 WebException 异常，处理返回的详细信息

try
{
    var request = (HttpWebRequest)WebRequest.Create(url);
    var response = (HttpWebResponse)request.GetResponse();
    ...
}
catch (WebException ex)
{
    var strError = ex.Message;
    using (WebResponse res = ex.Response)
    {
        var httpResponse = (HttpWebResponse)res;
        using (Stream data = res.GetResponseStream())
        {
            using (StreamReader reader = new StreamReader(data))
            {
                strError = reader.ReadToEnd();
            }
        }
        statusCode = httpResponse.StatusCode;
    }
    if (ex.Status != WebExceptionStatus.ProtocolError)
        throw;

    responseBody = strError;
}