Strange thing is going on with my HttpWebRequest...
I want to write a function that updates authorization header if needed (when we get 401 in response). So basically something like this:
try
{
request.Headers.Add(HttpRequestHeader.Authorization, "Bearer " + BadToken);
return request.GetResponse();
}
catch (Exception e)
{
if (e is WebException)
{
var ex = (e as WebException);
var status = (ex.Response as HttpWebResponse)?.StatusCode;
if (status == HttpStatusCode.Unauthorized)
{
request.Headers.Set(HttpRequestHeader.Authorization, "Bearer " + CorrectToken);
return request.GetResponse();
}
}
return null;
}
Unfortunately I still get a 401.
But if I replace BadToken with CorrectToken at the first line, I get 200 in first try. So it seems like the header is not updated... I checked in the debugger and I can see that value is changed, but the behaviour speaks for itself...
What is going on in here?
Multiple calls to GetResponse return the same response object; the request is not reissued. Refer this link: https://learn.microsoft.com/en-us/dotnet/api/system.net.httpwebrequest.getresponse?view=netframework-4.8
Make a new instance of HttpWebRequest in the catch block and issue the request with new token.
Related
I've found one thread on the Xamarin forums about the same issue, but the guy didn't get any responses, so I'm guessing this is a rare issue related to Xamarin (Android).
The code snippet below works perfectly fine if I use valid credentials, but if I use wrong credentials, or if there is any other reason why the app can't authenticate, a WebException is thrown (400 at wrong credentials, 500 at server error etc.).
The problem is that I don't know how to handle the exception, it throws the exception when it goes into the Post() method...
private void Authenticate()
{
if (Credentials != null && client.Authenticator == null)
{
RestClient authClient = new RestClient(client.BaseUrl);
RestRequest authRequest = new RestRequest("/token", Method.POST);
UserCredentials userCred = Credentials as UserCredentials;
if (userCred != null)
{
authRequest.AddParameter("grant_type", "password");
authRequest.AddParameter("username", userCred.UserName);
authRequest.AddParameter("password", userCred.Password);
}
var response = authClient.Post<AccessTokenResponse>(authRequest);
response.EnsureSuccessStatusCode();
client.Authenticator = new TokenAuthenticator(response.Data.AccessToken);
}
}
Server responses in the range of 4xx and 5xx throw a WebException. You need to catch it, get the status code from WebException and manage the response.
try{
response = (HttpWebResponse)authClient.Post<AccessTokenResponse>(authRequest);
wRespStatusCode = response.StatusCode;
}
catch (WebException we)
{
wRespStatusCode = ((HttpWebResponse)we.Response).StatusCode;
// ...
}
If you need the numeric value of the HttpStatusCode just use:
int numericStatusCode = (int)wRespStatusCode ;
You use a try..catch block to catch the Exception, then add whatever error handling logic is appropriate.
try {
var response = authClient.Post<AccessTokenResponse>(authRequest);
response.EnsureSuccessStatusCode();
} catch (WebException ex) {
// something bad happened, add whatever logic is appropriate to notify the
// user, log the error, etc...
Console.Log(ex.Message);
}
I am initiating an HttpWebRequest and then retrieving it's response. Occasionally, I get a 500 (or at least 5##) error, but no description. I have control over both endpoints and would like the receiving end to get a little bit more information. For example, I would like to pass the exception message from server to client. Is this possible using HttpWebRequest and HttpWebResponse?
Code:
try
{
HttpWebRequest webRequest = HttpWebRequest.Create(URL) as HttpWebRequest;
webRequest.Method = WebRequestMethods.Http.Get;
webRequest.Credentials = new NetworkCredential(Username, Password);
webRequest.ContentType = "application/x-www-form-urlencoded";
using(HttpWebResponse response = webRequest.GetResponse() as HttpWebResponse)
{
if(response.StatusCode == HttpStatusCode.OK)
{
// Do stuff with response.GetResponseStream();
}
}
}
catch(Exception ex)
{
ShowError(ex);
// if the server returns a 500 error than the webRequest.GetResponse() method
// throws an exception and all I get is "The remote server returned an error: (500)."
}
Any help with this would be much appreciated.
Is this possible using HttpWebRequest and HttpWebResponse?
You could have your web server simply catch and write the exception text into the body of the response, then set status code to 500. Now the client would throw an exception when it encounters a 500 error but you could read the response stream and fetch the message of the exception.
So you could catch a WebException which is what will be thrown if a non 200 status code is returned from the server and read its body:
catch (WebException ex)
{
using (var stream = ex.Response.GetResponseStream())
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
}
catch (Exception ex)
{
// Something more serious happened
// like for example you don't have network access
// we cannot talk about a server exception here as
// the server probably was never reached
}
I came across this question when trying to check if a file existed on an FTP site or not. If the file doesn't exist there will be an error when trying to check its timestamp. But I want to make sure the error is not something else, by checking its type.
The Response property on WebException will be of type FtpWebResponse on which you can check its StatusCode property to see which FTP error you have.
Here's the code I ended up with:
public static bool FileExists(string host, string username, string password, string filename)
{
// create FTP request
FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + host + "/" + filename);
request.Credentials = new NetworkCredential(username, password);
// we want to get date stamp - to see if the file exists
request.Method = WebRequestMethods.Ftp.GetDateTimestamp;
try
{
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
var lastModified = response.LastModified;
// if we get the last modified date then the file exists
return true;
}
catch (WebException ex)
{
var ftpResponse = (FtpWebResponse)ex.Response;
// if the status code is 'file unavailable' then the file doesn't exist
// may be different depending upon FTP server software
if (ftpResponse.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
{
return false;
}
// some other error - like maybe internet is down
throw;
}
}
I faced a similar situation:
I was trying to read raw response in case of an HTTP error consuming a SOAP service, using BasicHTTPBinding.
However, when reading the response using GetResponseStream(), got the error:
Stream not readable
So, this code worked for me:
try
{
response = basicHTTPBindingClient.CallOperation(request);
}
catch (ProtocolException exception)
{
var webException = exception.InnerException as WebException;
var rawResponse = string.Empty;
var alreadyClosedStream = webException.Response.GetResponseStream() as MemoryStream;
using (var brandNewStream = new MemoryStream(alreadyClosedStream.ToArray()))
using (var reader = new StreamReader(brandNewStream))
rawResponse = reader.ReadToEnd();
}
You can also use this library which wraps HttpWebRequest and Response into simple methods that return objects based on the results. It uses some of the techniques described in these answers and has plenty of code inspired by answers from this and similar threads. It automatically catches any exceptions, seeks to abstract as much boiler plate code needed to make these web requests as possible, and automatically deserializes the response object.
An example of what your code would look like using this wrapper is as simple as
var response = httpClient.Get<SomeResponseObject>(request);
if(response.StatusCode == HttpStatusCode.OK)
{
//do something with the response
console.Writeline(response.Body.Id); //where the body param matches the object you pass in as an anonymous type.
}else {
//do something with the error
console.Writelint(string.Format("{0}: {1}", response.StatusCode.ToString(), response.ErrorMessage);
}
Full disclosure
This library is a free open source wrapper library, and I am the author of said library. I make no money off of this but have found it immensely useful over the years and am sure anyone who is still using the HttpWebRequest / HttpWebResponse classes will too.
It is not a silver bullet but supports get, post, delete with both async and non-async for get and post as well as JSON or XML requests and responses. It is being actively maintained as of 6/21/2020
Sometimes ex.Response also throws NullReferenceException so below is the best way to handle
catch (WebException ex)
{
using (var stream = ex?.Response?.GetResponseStream())
if(stream != null)
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
// todo...
}
catch (Exception ex)
{
// todo...
}
**Answer Updated on 14-03-2022**
HttpWebRequest myHttprequest = null;
HttpWebResponse myHttpresponse = null;
try
{
myHttpRequest = (HttpWebRequest)WebRequest.Create(URL);
myHttpRequest.Method = "POST";
myHttpRequest.ContentType = "application/x-www-form-urlencoded";
myHttpRequest.ContentLength = urinfo.Length;
StreamWriter writer = new StreamWriter(myHttprequest.GetRequestStream());
writer.Write(urinfo);
writer.Close();
myHttpresponse = (HttpWebResponse)myHttpRequest.GetResponse();
if (myHttpresponse.StatusCode == HttpStatusCode.OK)
{
//Success code flow
}
myHttpresponse.Close();
}
catch(WebException e) {
Console.WriteLine("This program is expected to throw WebException on successful run."+
"\n\nException Message :" + e.Message);
if(e.Status == WebExceptionStatus.ProtocolError) {
Console.WriteLine("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
Console.WriteLine("Status Description : {0}",
((HttpWebResponse)e.Response).StatusDescription);
}
**Updated Answer with try catch block**
[docs.microsoft][1]
I am trying to swap my website over to consuming the new Twitter 1.1 API with uses OAuth 1.0a. I am able to get the correct response using a REST client and I am now trying to duplicate that on my website using c#.
I have constructed my headers the appropriate way and I have verified that they are in the correct format for what Twitter is looking for.
The issue I am having is that I do not think I am actually sending the request. I say this because my application returns almost instantly. The request should take a second or so to send at least, and my response has totally empty, with no 401 or 400 status code.
Below I have the code that actually sends the request. I am actually sending the request and if so why am I not getting any status code or anything.
Thanks in advance for the help.
//string url = "https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name=MYSCREENNAME&count=2";
string url = "https://api.twitter.com/1.1/statuses/user_timeline.json";
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.Method = "GET";
webRequest.Headers.Add("Authorization", authorizationHeaderParams);
try {
var response = webRequest.GetResponse() as HttpWebResponse;
if (response != null && response.StatusCode != HttpStatusCode.OK) {
lblresponse.InnerText = "The request did not complete and returned status code: {0} " + response.StatusCode;
}
if (response != null) {
var reader = new StreamReader(response.GetResponseStream());
reader.ReadToEnd();
lblresponse.InnerText += "success";
}
} catch {
lblresponse.InnerText += "fail";
}
So yeah this code goes straight to the catch block. My thoughts are I am not actually sending the request, since it takes no time to happen. I know there are some libraries designed to make this easier but I would much rather learn how to do it myself (with the help of you guys).
Thanks.
The request is going to throw an exception in the case of a 400 or 401. So catch System.Web.Exception in the catch block to see if there's a 400 or 401.
catch(System.Web.Exception ex) {
var errorReponse = (HttpWebResponse)ex.Response;
var statusCode = errorReponse.StatusCode;
lblresponse.InnerText += "fail";
}
I have a problem with httpwebrequest exception. I use the following code to make a request and catch the exception.
try
{
Uri url= new Uri("https://www.example.com");
HttpWebRequest request2 =(HttpWebRequest)WebRequest.Create(url);
request2.Timeout = 10000;
HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse();
response2.Close();
}
catch (TimeoutException)
{
listBox.Items.Insert(0, "Timeout");
}
catch (WebException ex)
{
using (WebResponse response = ex.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)response;
listBox.Items.Insert(0, "Status code(Benchmark):" + httpResponse.StatusCode);
}
}
catch
{
listBox.Items.Insert(0, "Failure");
}
At company network when I enter a non-existing url such as www.oiuahsdupiasduiuhid.com; it throws webexception . I got status code: not found or service unavailable. However If I try it at home, it doesn't throw any exception. It waits around 1 second and then without any error stops working. I delete all exceptions to see what is happening but the problem is it doesn’t show any error.
Do you have any idea about what is the problem?
Or any recommendation, how can I handle this problem with a different way?
Without knowing more about your application design, specifically exception handling further up the call stack, it is hard to say why it is behaving like it is when you are at home.
But when I just tried your exact code, it did throw a WebException, however httpResponse.StatusCode throws a NullReferenceException because httpResponse is null. If you are potentially swallowing this exception further up the call stack, it could explain the situation you are seeing.
httpResponse is going to be null in many WebException cases because your request did not receive any response, specifically in the timeout scenario.
Before casting WebException.Response, you need to check the WebException.Status property. If that status suggests a response was received, then you can go check WebException.Response, otherwise it is just going to be null. Try something like:
if(e.Status == WebExceptionStatus.ProtocolError) {
listBox.Items.Insert("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
}
else
{
listBox.Items.Insert("Status : {0}", ex.Status);
}
As a side note, your response2.Close(); is never going to be called when HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse(); throws an exception, so you should be wrapping it in a using block:
using(HttpWebResponse response2 = (HttpWebResponse)request2.GetResponse())
{
// do something with response
}
Thanks to psubsee2003. I got my answer. here is my code which is working properly. I added following codes to webexception.
if (ex.Status == WebExceptionStatus.ProtocolError)
{
using (WebResponse response = ex.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)response;
listBox2.Items.Insert(0, "Status:" + httpResponse.StatusCode);
}
}
else
{
listBox2.Items.Insert(0, "Status: " + ex.Status);
}
I am initiating an HttpWebRequest and then retrieving it's response. Occasionally, I get a 500 (or at least 5##) error, but no description. I have control over both endpoints and would like the receiving end to get a little bit more information. For example, I would like to pass the exception message from server to client. Is this possible using HttpWebRequest and HttpWebResponse?
Code:
try
{
HttpWebRequest webRequest = HttpWebRequest.Create(URL) as HttpWebRequest;
webRequest.Method = WebRequestMethods.Http.Get;
webRequest.Credentials = new NetworkCredential(Username, Password);
webRequest.ContentType = "application/x-www-form-urlencoded";
using(HttpWebResponse response = webRequest.GetResponse() as HttpWebResponse)
{
if(response.StatusCode == HttpStatusCode.OK)
{
// Do stuff with response.GetResponseStream();
}
}
}
catch(Exception ex)
{
ShowError(ex);
// if the server returns a 500 error than the webRequest.GetResponse() method
// throws an exception and all I get is "The remote server returned an error: (500)."
}
Any help with this would be much appreciated.
Is this possible using HttpWebRequest and HttpWebResponse?
You could have your web server simply catch and write the exception text into the body of the response, then set status code to 500. Now the client would throw an exception when it encounters a 500 error but you could read the response stream and fetch the message of the exception.
So you could catch a WebException which is what will be thrown if a non 200 status code is returned from the server and read its body:
catch (WebException ex)
{
using (var stream = ex.Response.GetResponseStream())
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
}
catch (Exception ex)
{
// Something more serious happened
// like for example you don't have network access
// we cannot talk about a server exception here as
// the server probably was never reached
}
I came across this question when trying to check if a file existed on an FTP site or not. If the file doesn't exist there will be an error when trying to check its timestamp. But I want to make sure the error is not something else, by checking its type.
The Response property on WebException will be of type FtpWebResponse on which you can check its StatusCode property to see which FTP error you have.
Here's the code I ended up with:
public static bool FileExists(string host, string username, string password, string filename)
{
// create FTP request
FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + host + "/" + filename);
request.Credentials = new NetworkCredential(username, password);
// we want to get date stamp - to see if the file exists
request.Method = WebRequestMethods.Ftp.GetDateTimestamp;
try
{
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
var lastModified = response.LastModified;
// if we get the last modified date then the file exists
return true;
}
catch (WebException ex)
{
var ftpResponse = (FtpWebResponse)ex.Response;
// if the status code is 'file unavailable' then the file doesn't exist
// may be different depending upon FTP server software
if (ftpResponse.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
{
return false;
}
// some other error - like maybe internet is down
throw;
}
}
I faced a similar situation:
I was trying to read raw response in case of an HTTP error consuming a SOAP service, using BasicHTTPBinding.
However, when reading the response using GetResponseStream(), got the error:
Stream not readable
So, this code worked for me:
try
{
response = basicHTTPBindingClient.CallOperation(request);
}
catch (ProtocolException exception)
{
var webException = exception.InnerException as WebException;
var rawResponse = string.Empty;
var alreadyClosedStream = webException.Response.GetResponseStream() as MemoryStream;
using (var brandNewStream = new MemoryStream(alreadyClosedStream.ToArray()))
using (var reader = new StreamReader(brandNewStream))
rawResponse = reader.ReadToEnd();
}
You can also use this library which wraps HttpWebRequest and Response into simple methods that return objects based on the results. It uses some of the techniques described in these answers and has plenty of code inspired by answers from this and similar threads. It automatically catches any exceptions, seeks to abstract as much boiler plate code needed to make these web requests as possible, and automatically deserializes the response object.
An example of what your code would look like using this wrapper is as simple as
var response = httpClient.Get<SomeResponseObject>(request);
if(response.StatusCode == HttpStatusCode.OK)
{
//do something with the response
console.Writeline(response.Body.Id); //where the body param matches the object you pass in as an anonymous type.
}else {
//do something with the error
console.Writelint(string.Format("{0}: {1}", response.StatusCode.ToString(), response.ErrorMessage);
}
Full disclosure
This library is a free open source wrapper library, and I am the author of said library. I make no money off of this but have found it immensely useful over the years and am sure anyone who is still using the HttpWebRequest / HttpWebResponse classes will too.
It is not a silver bullet but supports get, post, delete with both async and non-async for get and post as well as JSON or XML requests and responses. It is being actively maintained as of 6/21/2020
Sometimes ex.Response also throws NullReferenceException so below is the best way to handle
catch (WebException ex)
{
using (var stream = ex?.Response?.GetResponseStream())
if(stream != null)
using (var reader = new StreamReader(stream))
{
Console.WriteLine(reader.ReadToEnd());
}
// todo...
}
catch (Exception ex)
{
// todo...
}
**Answer Updated on 14-03-2022**
HttpWebRequest myHttprequest = null;
HttpWebResponse myHttpresponse = null;
try
{
myHttpRequest = (HttpWebRequest)WebRequest.Create(URL);
myHttpRequest.Method = "POST";
myHttpRequest.ContentType = "application/x-www-form-urlencoded";
myHttpRequest.ContentLength = urinfo.Length;
StreamWriter writer = new StreamWriter(myHttprequest.GetRequestStream());
writer.Write(urinfo);
writer.Close();
myHttpresponse = (HttpWebResponse)myHttpRequest.GetResponse();
if (myHttpresponse.StatusCode == HttpStatusCode.OK)
{
//Success code flow
}
myHttpresponse.Close();
}
catch(WebException e) {
Console.WriteLine("This program is expected to throw WebException on successful run."+
"\n\nException Message :" + e.Message);
if(e.Status == WebExceptionStatus.ProtocolError) {
Console.WriteLine("Status Code : {0}",
((HttpWebResponse)e.Response).StatusCode);
Console.WriteLine("Status Description : {0}",
((HttpWebResponse)e.Response).StatusDescription);
}
**Updated Answer with try catch block**
[docs.microsoft][1]