Develop Reference

WebException details changed on VS.Net

A Rest API call throws an exception on post. And that is
The remote server returned an error: (404) Not Found.
The following code calling the api
try
{
RestClient client = new RestClient(...);
string apiResponse = client.MakeRequest(..);
}
catch (WebException wex)
{
throw wex;
}
It works fine when the fiddler is capturing traffic. But if the fiddler is not capturing then client received the following exception.
The remote server returned an error: (502) Bad Gateway.
PS. Postman (Chrome extension) and Soap UI also received 404: Not Found
UPDATED:
This is the code and the error is received while debugging
public string MakeRequest(string parameters)
{
var request = (HttpWebRequest)WebRequest.Create(_RestEndPoint + (parameters ?? String.Empty));
request.Proxy = WebRequest.DefaultWebProxy;
request.ContentLength = 0;
request.Method = _Method.ToString();
request.ContentType = _ContentType;
request.KeepAlive = true;
if (_RequestHeader != null)
{
foreach (var hdr in _RequestHeader)
{
request.Headers.Add(hdr.Key, hdr.Value);
}
}
if (_Method == HttpVerb.POST || _Method == HttpVerb.PUT)
{
if (!string.IsNullOrEmpty(_PayLoad))
{
var bytes = Encoding.UTF8.GetBytes(_PayLoad);
request.ContentLength = bytes.Length;
using (var writeStream = request.GetRequestStream())
{
writeStream.Write(bytes, 0, bytes.Length);
writeStream.Close();
}
}
}
using (var response = (HttpWebResponse)request.GetResponse())//Error returns here
{
var responseValue = string.Empty;
checkForResponseExceptions(response.StatusCode, parameters);
// grab the response
using (var responseStream = request.GetResponse().GetResponseStream())
{
if (responseStream != null)
{
using (var reader = new StreamReader(responseStream))
{
responseValue = reader.ReadToEnd();
}
}
}
return responseValue;
}
}
Can anyone please point out what am i missing?
Update 2:
I have tried the following code and have the same issue
if (_Method == HttpVerb.POST)
{
using (var wb = new WebClient())
{
wb.Headers[HttpRequestHeader.ContentType] = _ContentType;
foreach (var hdr in _RequestHeader)
{
wb.Headers.Add(hdr.Key, hdr.Value);
}
try
{
var response = wb.UploadString(_RestEndPoint + (parameters ?? String.Empty), _Method.ToString(), _PayLoad);
}
catch (Exception ex)
{
throw ex;
}
}
}
So, I guess something is wrong in the network settings as #GSerg commented on Dec 4 at 10:01. But there are no proxy set up in connection tab of IE settings. What and how should i check to get rid of this problem??

HTTP errors are grouped by "type of errors"
4xx errors are "client" errors, errors that are linked to the user doing a mistake, like 404 is the client asking for something that does not exist on the server.
5xx errors are "server" errors, meaning that the server had a problem answering the request, because of internal issues.
The 502 bad gateway is usually sent from a server when he couldn't get a request from another server. In your case, it could be coming from fiddler, because you're probably still making the query to fiddler who is stopped, and thus cannot answer.

Uri.IsWellFormedUriString returns true, but cannot read from a url

I am trying to check if the url http://master.dev.brandgear.net is valid by the following method:
private bool UrlIsValid(string url)
{
using (var webClient = new WebClient())
{
bool response;
try
{
webClient.UseDefaultCredentials = true;
using (Stream strm = webClient.OpenRead(url))
{
response = true;
}
}
catch (WebException we)
{
response = false;
}
return response;
}
}
However, I am getting a web exception "404 not found.". I have checked the uri with Uri.IsWellFormedUriString and it is returning true. However, the same url can be opened through a browser. Any idea how to validate it?

I ran your example with following URL http://master.dev.brandgear.net and exception is also raised. If you open same URL in browser (for example Firefox) and run Firebug plugin, open Network tab you will see error 404 (Page not found). Your code is OK, but server returns 404.

To really get a response, you have to use WebException instead of GetResponse or GetResponseStream methods when the 404 exception happens.Also use HttpWebRequest and HttpWebResponse in these situations for better control,so after the exception occurs you check its state to see if its a ProtocolError and if so get the response from there:
private bool UrlIsValid(string url)
{
bool response = false;
HttpWebResponse rep = null;
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
rep = (HttpWebResponse)request.GetResponse();
}
catch (WebException we)
{
if (we.Status == WebExceptionStatus.ProtocolError)
rep = (HttpWebResponse)we.Response;
}
if (rep != null)
{
try
{
using (Stream strm = rep.GetResponseStream())
{
response = true;
}
}
catch (WebException ex)
{
//no need variable is already false if we didnt succeed.
//response = false;
}
}
return response;
}

Catching HttpWebRequest Timeout

public int loginEmail(string email, string password)
{
HttpWebRequest request = null;
string responseStr = null;
string Email = email;
string Pass = password;
UTF8Encoding encoding = new UTF8Encoding();
string postData = "PostData";
byte[] data = encoding.GetBytes(postData);
request = (HttpWebRequest)WebRequest.Create("url");
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.AllowAutoRedirect = false;
request.KeepAlive = false;
request.Proxy = null;
request.ServicePoint.ConnectionLimit = 1000;
request.ContentLength = data.Length;
request.Timeout = 5000;
request.ServicePoint.ConnectionLeaseTimeout = 5000;
request.ServicePoint.MaxIdleTime = 5000;
using (Stream stream = request.GetRequestStream())
{
stream.Write(data, 0, data.Length);
}
try
{
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
responseStr = response.Headers["Set-Cookie"];
}
}
catch
{
return 1;
}
string[] cooktemp;
string[] seperatortemp = new string[] { ";" };
cooktemp = responseStr.Split(seperatortemp, StringSplitOptions.None);
LoginHeaders[0] = cooktemp[0] + ";";
return 0;
}
This code runs just fine, but sometimes the request does not get a response back. When the request doesn't get a response back the program will hang and then finally it will give a timeout error that crashes the program. All I am trying to do right now is just catch the timeout error so I can handle it, but nothing seems to be catching it.

It is most likely timing out in GetRequestStream(). The documentation specifically states that it may throw WebException if the time-out period for the request expired.
So include that block of code inside your try/catch and you should be able to catch it.

This is an old thread, but an issue which I also hit today.
What I didn't realise is that if you have a web service which, say, attempts to write to a file which is locked... then having the code in a simple try..catch is not enough.
You must specifically have a catch which handles WebExceptions.
try
{
// Run your web service code
}
catch (WebException ex)
{
// Handle a WebException, such as trying to write to a "locked" file on the network
}
catch (Exception ex)
{
// Handle a regular Exception
}
I always thought that a WebException was a type of Exception, so these would get caught by this catch handler:
catch (Exception ex)
{
// Handle a regular Exception
}
It doesn't.
So to avoid your code throwing "Request timed out" messages, with no suggestion about what caused them, do remember to add these second catch handler.
Btw, on my web services tutorial, here's the code I recommend, which looks out for Exceptions, and returns them in the Response header:
try
{
// Put your code in here
}
catch (WebException ex)
{
// Return any exception messages back to the Response header
OutgoingWebResponseContext response = WebOperationContext.Current.OutgoingResponse;
response.StatusCode = System.Net.HttpStatusCode.InternalServerError;
response.StatusDescription = ex.Message.Replace("\r\n", "");
return null;
}
catch (Exception ex)
{
// Return any exception messages back to the Response header
OutgoingWebResponseContext response = WebOperationContext.Current.OutgoingResponse;
response.StatusCode = System.Net.HttpStatusCode.InternalServerError;
response.StatusDescription = ex.Message.Replace("\r\n", "");
return null;
}

try { ... }
catch (System.Net.WebException sne)
{
MessageBox.Show(req.Timeout.ToString());
}
I think the timeout will always be "5000" no matter what.
If you tell it "timeout is 5 seconds" it will always try for 5 seconds before giving up.

C# How can I get server error from a URL?

We have a url and we need to check whether web page is active or not. We tried following code:
WebResponse objResponse = null;
WebRequest objRequest = HttpWebRequest.Create(URL);
objRequest.Method = "HEAD";
try
{
objResponse = objRequest.GetResponse();
objResponse.Close();
}
catch (Exception ex)
{
}
Above code gave exception if unable to get a response but also works fine even if we have a "server error" on that page? Any help how to get server error?

The HttpResponse class has a StatusCode property which you can check. If it's 200 everything is ok.
You can change your code to this:
HttpWebResponse objResponse = null;
var objRequest = HttpWebRequest.Create("http://google.com");
objResponse = (HttpWebResponse) objRequest.GetResponse();
if(objResponse.StatusCode != HttpStatusCode.OK)
{
Console.WriteLine("It failed");
}else{
Console.WriteLine("It worked");
}

For one thing, use a using statement on the response - that way you'll dispose of it whatever happens.
Now, if a WebException is thrown, you can catch that and look at WebException.Response to find out the status code and any data sent back:
WebRequest request = WebRequest.Create(URL);
request.Method = "HEAD";
try
{
using (WebResponse response = request.GetResponse())
{
// Use data for success case
}
}
catch (WebException ex)
{
HttpWebResponse errorResponse = (HttpWebResponse) ex.Response;
HttpStatusCode status = errorResponse.StatusCode;
// etc
}

System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive

I'm trying to create a method in C# to return a string of a web pages html content from the url. I have tried several different ways, but I am getting the error System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive.
The following works fine locally, but gets the above error when running on a remote server:
public static string WebPageRead(string url)
{
string result = String.Empty;
WebResponse response = null;
StreamReader reader = null;
try
{
if (!String.IsNullOrEmpty(url))
{
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = false;
request.ProtocolVersion = HttpVersion.Version10;
response = request.GetResponse();
reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
result = reader.ReadToEnd();
}
}
catch (Exception exc)
{
throw exc;
}
finally
{
if (reader != null)
{
reader.Close();
}
if (response != null)
{
response.Close();
}
}
return result;
}

This is probably not the problem, but try the following:
public static string WebPageRead(string url)
{
if (String.IsNullOrEmpty(url))
{
return null;
}
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
if (request == null)
{
return null;
}
request.Method = "GET";
request.KeepAlive = false;
request.ProtocolVersion = HttpVersion.Version10;
using (WebResponse response = request.GetResponse())
{
using (Stream stream = response.GetResponseStream())
{
using (StreamReader reader =
new StreamReader(stream, Encoding.UTF8))
{
return reader.ReadToEnd();
}
}
}
}
I echo the earlier answer that suggests you try this with a known good URL. I'll add that you should try this with a known good HTTP 1.1 URL, commenting out the line that sets the version to 1.0. If that works, then it narrows things down considerably.

Thanks for the responses, the problem was due to a DNS issue on the remote server! Just to confirm, I went with the following code in the end:
public static string WebPageRead(string url)
{
string content = String.Empty;
if (!String.IsNullOrEmpty(url))
{
HttpWebRequest request = HttpWebRequest.Create(url) as HttpWebRequest;
if (request != null)
{
request.Method = "GET";
request.KeepAlive = false;
request.ProtocolVersion = HttpVersion.Version10;
try
{
using (WebResponse response = request.GetResponse())
{
using (Stream stream = response.GetResponseStream())
{
using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
{
content = reader.ReadToEnd();
}
}
}
}
catch (Exception exc)
{
throw exc;
}
}
}
return content;
}

Had a problem like this before that was solved by opening the url in IE on the machine with the problem. IE then asks you whether you want to add the url to the list of secure sites. Add it and it works for that url.
This is just one of the possible causes. Seriously a lot of other problems could cause this. Besides the problem described above, the best way I've found to solve this is the just catch the exception and retry the request.