Develop Reference

API WebService Not responding anything

This is basically my first API handling with C#, so I read and tried to create so I can handle the JSON, but I ain't getting any response, tried to display it in a label text, but I am not getting any error nor any response.
It is supposed to show the JSON in a label with answer with basic auth, so then, I can handle it, because I have been able to see the JSON if I log via POSTMAN, but if I run the code, all I see is nothing, even tho it is wrapped in a string.
public partial class callUni : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string strResponse = string.Empty;
strResponse = makeRequest();
answer.Text = strResponse;
}
public string makeRequest()
{
string strRequest = string.Empty;
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(#"https://unicard-api.asf.edu.mx:8443/api/Acessos/Entradas");
request.Credentials = GetCredential();
request.PreAuthenticate = true;
request.Method = httpMethod.ToString();
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
if (response.StatusCode != HttpStatusCode.OK)
{
throw new ApplicationException("error code = " + response.StatusCode);
}
//Vamos a procesar el JSON que viene de UNICARD
using (Stream responseStream = response.GetResponseStream())
{
if (responseStream != null)
{
using (StreamReader reader = new StreamReader(responseStream))
{
strRequest = reader.ReadToEnd();
}
}
}
}
}
catch (Exception e) { };
return strRequest;
}
private CredentialCache GetCredential()
{
string url = #"https://unicard-api.asf.edu.mx:8443/api/Acessos/Entradas";
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
CredentialCache credentialCache = new CredentialCache();
credentialCache.Add(new System.Uri(url), "Basic", new NetworkCredential(ConfigurationManager.AppSettings["xxxxx"], ConfigurationManager.AppSettings["xxxx"]));
return credentialCache;
}
}
}

You say "I am not getting any error nor any response.", but I think you are getting an error, but your line here is hiding it from you:
catch (Exception e) { };
Try either logging or displaying e.ToString() inside the catch block then investigating from there.
As a sidenote, Microsoft explicitly says not to throw ApplicationException. Either find a more relevant Exception class to use or throw Exception. https://msdn.microsoft.com/en-us/library/system.applicationexception%28v=vs.110%29.aspx#Remarks

Properly handle WebRequests

I have a dynamic page with a .JSON file, and I'm using my C# program to access it every x number of seconds, to determine if something has been changed or not. Everything works flawlessly as long as I have Internet connection, if for whatever reason I lose it, then my program crashes as the ex.Response is a null. I was wondering if there's a better way of handling the following code:
void Function(){
while(true){
jList = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<jsonList>(GET(jsonUrl));
//SOME THINGS I DO with the data above here
Thread.Sleep(5000);
}}
string GET(string url)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
try
{
WebResponse response = request.GetResponse();
using (Stream responseStream = response.GetResponseStream())
{
StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
return reader.ReadToEnd();
}
}
catch (WebException ex)
{
WebResponse errorResponse = ex.Response;
if (ex.Response != null) {
using (Stream responseStream = errorResponse.GetResponseStream())
{
StreamReader reader = new StreamReader(responseStream, Encoding.GetEncoding("utf-8"));
String errorText = reader.ReadToEnd();
// log errorText
}
}
throw;
}
}
Perhaps I should ping it first, and see if I get a reply, and only then Perform the WebRequest function?
EDIT:
After adding this
public bool getResponse(string URL)
{
try
{
WebClient wc = new WebClient();
string HTMLSource = wc.DownloadString(URL);
return true;
}
catch (Exception)
{
return false;
}
}
And use it as
void Function(){
while(true){
if (!getResponse(jsonUrl))
{
return;
}
jList = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<jsonList>(GET(jsonUrl));
//SOME THINGS I DO with the data above here
Thread.Sleep(5000);
}}
My C# application waits a bit, and then exits normally. Why?
The program '[10476] Kiosk2.vshost.exe' has exited with code 0 (0x0).

Alright, well this seems to work fine for me.
public void Update() //CALLED IT void FUNCTION earlier
{
while (true)
{
while (getResponse(jsonUrl))
{
jList = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<jsonList>(GET(jsonUrl));
//I DO SOME STUFF HERE
//INTERESTING STUFF
Thread.Sleep(5000);
}
}
}
And seconds function:
public bool getResponse(string URL)
{
try
{
WebClient wc = new WebClient();
string HTMLSource = wc.DownloadString(URL);
return true;
}
catch (Exception)
{
return false;
}
}

C# - Catch WebException While Posting XML Async

I am POSTING XML data using WebClient.
public string uploadXMLData(string destinationUrl, string requestXml)
{
try
{
System.Uri uri = new System.Uri(destinationUrl);
using (WebClient client = new WebClient())
{
client.Headers.Add("content-type", "text/xml");
var response = client.UploadString(destinationUrl, "POST", requestXml);
}
}
catch (WebException webex)
{
WebResponse errResp = webex.Response;
using (Stream respStream = errResp.GetResponseStream())
{
StreamReader reader = new StreamReader(respStream);
string text = reader.ReadToEnd();
}
}
catch (Exception e)
{ }
return null;
}
When there is an error, I catch it as WebException, and I read the Stream in order to know what the XML response is.
What I need to do, is post the XML data to the URL in Async.
So I changed the function:
public string uploadXMLData(string destinationUrl, string requestXml)
{
try
{
System.Uri uri = new System.Uri(destinationUrl);
using (WebClient client = new WebClient())
{
client.UploadStringCompleted
+= new UploadStringCompletedEventHandler(UploadStringCallback2);
client.UploadStringAsync(uri, requestXml);
}
}
catch (Exception e)
{ }
return null;
}
void UploadStringCallback2(object sender, UploadStringCompletedEventArgs e)
{
Console.WriteLine(e.Error);
}
How can I catch the WebException now and read the XML response?
Can I throw e.Error?
Any help would be appreciated

I found the solution:
void UploadStringCallback2(object sender, UploadStringCompletedEventArgs e)
{
if (e.Error != null)
{
object objException = e.Error.GetBaseException();
Type _type = typeof(WebException);
if (_type != null)
{
WebException objErr = (WebException)e.Error.GetBaseException();
WebResponse rsp = objErr.Response;
using (Stream respStream = rsp.GetResponseStream())
{
StreamReader reader = new StreamReader(respStream);
string text = reader.ReadToEnd();
}
throw objErr;
}
else
{
Exception objErr = (Exception)e.Error.GetBaseException();
throw objErr;
}
}
}

How to catch exception?

I am trying to call api and check its response, but when ever some wrong value is passed it stops the program. I want to add exception during request and response but not sure how to write in function.
This is how i call my REST call
public dynamic APICalls(JObject ljson, string endpoints, string method)
{
var httpReq = (HttpWebRequest)HttprequestObject(endpoints, method);
using (var streamWriter = new StreamWriter(httpReq.GetRequestStream()))
{
streamWriter.Write(ljson);
streamWriter.Flush();
streamWriter.Close();
}
var httpResponse = (HttpWebResponse)httpReq.GetResponse();
var result = "";
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
result = streamReader.ReadToEnd();
}
return result;
//return "Success";
//not sure what to return
//here i have to add sql server code to enter into database
}
THis is code for request
public dynamic HttprequestObject(string endpoints, string method)
{
string url = Settings.API_TEST_VALUE + endpoints;
var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
httpWebRequest.ContentType = "application/json";
httpWebRequest.Method = method;
return httpWebRequest;
}
And right before request and right after response i want to catch exception.
At this point i have to catch exception
var httpResponse = (HttpWebResponse)httpReq.GetResponse();
If some one gives me hint how to catch that before it stops program.
There are 400, 401,402 errors, if something is wrong API sends json
For instance, while creating user :-- Email id already exists
But that points stops json and stops program..
Using try catch it will stop program, I want it to run and want to receive resposne.
Actually, API will send error .
For instance, status will be ;---401 UNAUTHORIZED
and resposnse will be
{ "reason": "Email already registered.", "success": false }
I am changed my code and
HttpWebResponse httpResponse;
try
{
//HttpWebResponse myHttpWebResponse = (HttpWebResponse)httpReq.GetResponse();
httpResponse = (HttpWebResponse)httpReq.GetResponse();
//myHttpWebResponse.Close();
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
result = streamReader.ReadToEnd();
}
}
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);
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
return result;
//return "Success";
//not sure what to return
//here i have to add sql server code to enter into database
}
This is the new code, but I m not getting Json as return value, So i can show specific error.
For below Json what should I write?
{ "reason": "Email already registered.", "success": false }
please I m new to c# and if something is not clear please modify or ask question?
thank you

What you're looking for is called a try-catch statement:
try
{
var httpResponse = (HttpWebResponse)httpReq.GetResponse();
}
catch (WebException e)
{
// Here is where you handle the exception.
}
Using WebException as the type in the catch statement means only exceptions of that particular type will be caught.
In case an exception occurs, the e variable will contain exception details, such as a message passed from the method which three the exception and any inner exceptions encapsulated inside.

You can handle your web exceptions to get HttpStatusCode and Response Message this way:
public void SendAndGetResponseString()
{
try
{
// Here you call your API
}
catch (WebException e)
{
var result = GetResponceFromWebException(e);
if (result != null){
//
// Here you could use the HttpStatusCode and HttpResponseMessage
//
}
throw;
}
catch (Exception e)
{
// log exception or do nothing or throw it
}
}
private HttpRequestResponce GetResponceFromWebException(WebException e)
{
HttpRequestResponce result = null;
if (e.Status == WebExceptionStatus.ProtocolError)
{
try
{
using (var stream = e.Response.GetResponseStream())
{
if (stream != null)
{
using (var reader = new StreamReader(stream))
{
var responseString = reader.ReadToEnd();
var responce = ((HttpWebResponse) e.Response);
result = new HttpRequestResponce(responseString, responce.StatusCode);
}
}
}
}
catch (Exception ex)
{
// log exception or do nothing or throw it
}
}
return result;
}
public class HttpRequestResponce {
public HttpStatusCode HttpStatusCode { get;set; }
public string HttpResponseMessage {get;set;}
public HttpRequestResponce() { }
public HttpRequestResponce(string message, HttpStatusCode code)
{
HttpStatusCode=code;
HttpResponseMessage=message;
}
}

You encapsulate whatever method call or code block you want to prevent from throwing unhandled exceptions.
try
{
// code here
}
catch (Exception)
{
// here you may do whatever you want to do when an exception is caught
}

Ok,Finally I am able to Solve this.. Thanks everyone for you help.
This worked for me. I think I was not reading whole response.. So some how I think I realized and now its working ..
HttpWebResponse httpResponse;
try
{
httpResponse = (HttpWebResponse)httpReq.GetResponse();
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
{
result = streamReader.ReadToEnd();
}
}
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);
using (Stream data = e.Response.GetResponseStream())
using (var reader = new StreamReader(data))
{
string text = reader.ReadToEnd();
Console.WriteLine(text);
}
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}

How to Send POST Request in windows Phone 8 and get its Response in json

I am trying to call a web service
which returns a JSON response. So far my code is working fine for GET Request but now services on server are POST and I have no idea how to do that! Below is the code for GET Request:
private void callSigninWebservice()
{
setProgressIndicator(true);
SystemTray.ProgressIndicator.Text = "Signing in please wait";
try
{
WebClient webClient = new WebClient();
Uri uri = new Uri(GlobalVariables.URL_USER +
GlobalVariables.URL_STUDENT_SIGNIN_MODE_LOGIN +
GlobalVariables.URL_EMAIL + tbUsername.Text +
GlobalVariables.URL_PASSWORD + tbPassword.Password);
webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(webClient_DownloadStringCompleted);
webClient.DownloadStringAsync(uri);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message + "error came here 1");
}
}
For Response
void webClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
try
{
JObject parentObj = JObject.Parse(e.Result);
String strResult = (String)parentObj[SigninData.JSON_result];
bool bolresult = strResult.Equals(SigninData.JSON_result_success, StringComparison.Ordinal);
if (bolresult)
{
JObject dataObj = (JObject)parentObj[SigninData.JSON_data];
setUserData(dataObj);
NavigationService.Navigate(new Uri("/BasePage.xaml", UriKind.RelativeOrAbsolute));
}
else
{
String error = (String)parentObj[SigninData.JSON_data];
MessageBox.Show("Error : " + error);
}
setProgressIndicator(false);
}
catch (Exception)
{
setProgressIndicator(false);
}
}

This is a simple way of making a post request and receiving a response in JSON for future parse:
internal static async Task<String> GetHttpPostResponse(HttpWebRequest request, string postData)
{
String received = null;
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
byte[] requestBody = Encoding.UTF8.GetBytes(postData);
// ASYNC: using awaitable wrapper to get request stream
using (var postStream = await request.GetRequestStreamAsync())
{
// Write to the request stream.
// ASYNC: writing to the POST stream can be slow
await postStream.WriteAsync(requestBody, 0, requestBody.Length);
}
try
{
// ASYNC: using awaitable wrapper to get response
var response = (HttpWebResponse)await request.GetResponseAsync();
if (response != null)
{
var reader = new StreamReader(response.GetResponseStream());
// ASYNC: using StreamReader's async method to read to end, in case
// the stream i slarge.
received = await reader.ReadToEndAsync();
}
}
catch (WebException we)
{
var reader = new StreamReader(we.Response.GetResponseStream());
string responseString = reader.ReadToEnd();
Debug.WriteLine(responseString);
return responseString;
}
return received;
}