System.Net.WebException is not being caught

Question

I have a strange issue happening. I have some code which must do an http post to a client's server. Their post returns content to me, which I need to show to my user. If thee is a problem, I want to trap the error and inject my own content to let the user know there was a problem.

Here is my static helper class for performing the http post.

public static class HttpPostHelper
{
    public static string Post(string url, NameValueCollection values)
    {
        StringBuilder dataBuilder = new StringBuilder();

        foreach (var key in values.AllKeys)
        {
            EncodeAndAddItem(ref dataBuilder, key, values[key]);
        }

        Uri uri = new Uri(url);
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = dataBuilder.Length;
        using (Stream writeStream = request.GetRequestStream())
        {
            UTF8Encoding encoding = new UTF8Encoding();
            byte[] bytes = encoding.GetBytes(dataBuilder.ToString());
            writeStream.Write(bytes, 0, bytes.Length);
        }

        string result = String.Empty;

        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            using (Stream responseStream = response.GetResponseStream())
            {
                using (StreamReader readStream = new StreamReader(responseStream, Encoding.UTF8))
                {
                    result = readStream.ReadToEnd();
                }
            }
        }

        return result;
    }

    private static void EncodeAndAddItem(ref StringBuilder baseRequest, string key, string dataItem)
    {
        if (baseRequest == null)
        {
            baseRequest = new StringBuilder();
        }
        if (baseRequest.Length != 0)
        {
            baseRequest.Append("&");
        }

        baseRequest.Append(key);
        baseRequest.Append("=");
        baseRequest.Append(System.Web.HttpUtility.UrlEncode(dataItem));
    }
}

And here is my code that does the post and returns the content.

private string GetReturnContent(string callback, NameValueCollection data, LogRequest request)
{
    string content = String.Empty;

    try
    {
        
        content = HttpPostHelper.Post(callback, data);
        
        request.Message = String.Format("Content Retrieved from Callback: {0}", content);

        logService.Debug(request);
    }
    catch (System.Net.WebException ex)
    {
        var response = ex.Response as HttpWebResponse;

        if (response != null)
        {
            if ((int)response.StatusCode == 403)
            {
                content = String.Format("The url {0} returned access denied (403).", callback);
                request.Message = content;
                logService.Warn(request);
            }
            else if ((int)response.StatusCode == 404)
            {
                content = String.Format("The url {0} returned page not found (404).", callback);
                request.Message = content;
                logService.Warn(request);
            }
            else if ((int)response.StatusCode == 405)
            {
                content = String.Format("The url {0} returned 405 error.  Please ensure the url is configured to accept http POST requests", callback);
                request.Message = content;
                logService.Warn(request);
            }
            else if ((int)response.StatusCode == 500)
            {
                content = String.Format("The url {0} returned a server error (500).", callback);
                request.Message = content;
                logService.Warn(request);
            }
            else
            {
                exceptionHandler.HandleError(ex);

                content = String.Format("The url {0} returned an error: {1}", callback, ex.Message);
                request.Message = content;
                logService.Error(request);
            }
        }
        else
        {
            exceptionHandler.HandleError(ex);

            content = String.Format("The url {0} returned an error: {1}", callback, ex.Message);
            request.Message = content;
            logService.Error(request);
        }
    }

    return content;
}

The problem is that no matter what, I always get a server error reported to me (through an e-mail reporting handler, but that is another story. I have the exception caught, and I am not re-throwing it, and yet I still get an error report.

Exception:

System.Net.WebException : Unable to connect to the remote server

Inner Exception Message:

System.Net.Sockets.SocketException : A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond [redacted]

The stack trace points to this line as the culprit in my PostHelper

using (Stream writeStream = request.GetRequestStream())

at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context) at System.Net.HttpWebRequest.GetRequestStream()

Answer 1

You are getting a socket error. This error is happening before HTTP traffic is sent (hence, no status codes).

This block is going to get executed (hence your error email notification):

exceptionHandler.HandleError(ex);

content = String.Format("The url {0} returned an error: {1}", callback, ex.Message);
request.Message = content;
logService.Error(request);