I am facing an issue with my application, whenever i click on any routerLink there is a rare case under which an exception arises and my app stops working until i reload it. Please suggest me a way to handle that exception and reload my app when it arises.
Thankyou.
You can have a new navigation method which will override the existing one and there you can use exception handling (try/ catch). Now you can catch the exception thrown by angular/javascript and reload you page.
Related
I have a global error handling for the controller which is working fine. But sometimes when any web.config element are missing or can't able to load it shows the error screen and hitting the application-error in the global.asax as the the exception never reaches the pipe line. Also I was able to redirect to a custom error page by setting custom error as remoteonly with redirection page but not able to log it as not hitting application-error in global.asax. Does anyone know how to handle the exception here
I guess, Exception handles your code only, the exception which you were taking is before any code to be execute and it will handle by Web Server i.e. IIS
I have a webform that has a single page method. My other web apps log unhandled exceptions to the system event log on the web server. Since the other developers that I work with expect to see entries for app errors in the event log, I would like this app to do the same.
However, I have the app send error emails when an exception is caught from calling code inside the page method. It is not writing to the event log when this occurs. Note: the page method re-throws the exception after calling my email notification method.
From what I've read so far it seems that ASP.Net logs errors to the event log by default. I imagine that the same is not true for Page Methods/WebMethods because they basically throw the exception to the client code calling it.
Is there a trivial way to have that exception bubble up properly so that it writes to the event log? No other apps write to the event log directly from what I've seen so I don't think the application could create a new source since our security people keep a lot of things locked down (with good intentions, yay security).
[WebMethod]
public static object MyPseudoWebMethod()
{
try
{
// My exception spawning unreliable code here
}
catch(Exception ex)
{
// Cleanup ...
this.SendErrorNotification(ex);
throw; // <-- This doesn't bubble up but I'd love for it to!
}
}
Hmm interesting problem. You are right in that WebMethod exceptions do NOT follow normal exception flow.
The Application_Error event is not fired if your web method throws an
exception. The reason for this is that the HTTP handler for XML Web
services consumes any exception that occurs while an XML Web service
is executing and turns it into a SOAP fault prior to the
Application_Error event is called.
(from here)
The above page suggests using a SOAP extension to catch that exception before its swallowed, but here's how I'd do it if you don't want to do that:
1) Make a new 'error recieving' ASPX page that you will build that will take whatever params you want to record in your error log. So for example, have this page take in a POST named "ExceptionDetails" or whatever else you wish to capture. This page will NOT be viewed directly in a browser, so it doesnt need any ASPX controls or anything, but using a MasterPage on it won't hurt anything.
2) In the code behind of this new page, grab whatever POSTS you are sending in and new-up an Exception with whatever details you need. Immediate throw this exception. Doing this means that this exception will follow whatever flow other unhandled exceptions follow in the app (logging, emailing, etc).
3) On the page that calls the WebMethod JS, Wrap the calls to the WebMethod in a try-catch
4) In the catch block, print out whatever message you want in the browser, and initiate a new AJAX post to that new error receiving ASPX page, passing along whatever POST stuff you made that page look for.
The new AJAX call will NOT change ANYTHING in the user's perception by default. The AJAX call fires off a new request to that page, and the ASPX page itself is actually totally unaware that its AJAX and not a normal browser request. Any cookies/session/authentication data that's currently set are available to the AJAXed page as well, if you are recording a user's ID or anything. If you look at the returned response from a tool like Firebug, you will see that its actually the YellowScreenOfDeath's HTML (unless you have a custom 500 page, in which case its that HTML that comes back).
This is simply how the legacy ASMX web services work.
The only workaround is to stop using them (which you should do anyway, unless you're stuck with .NET 2.0). WCF doesn't have this problem.
I am using .net framework 4.0, plain asp.net and working with webform. Currently I having a base class to handle all parameter passing and redirect. I wonder is it possible to write a base class to handle nullRefeerenceException from all pages in once, lets say redirect end user to somewhere or display particular error message.
Scenario: For example, some pages must come along with parameter, if no parameter captured, I would like to redirect them to somewhere.
You can try to control the ProcessRequest. You need to test it to see if can do the work you ask for, but this is a good point to capture all errors of your page.
public override void ProcessRequest(HttpContext context)
{
try
{
base.ProcessRequest(context);
}
catch (Exception x)
{
// handle here your error from the page...
}
}
Some more notes
I was use this code on one critical page, but I do not use it for all my page. Even tho can capture the errors, some times you can not do nothing else here other than throw again the final error, so end up that is better to log your unknown and unhandled errors from globa.asax Application_Error, and on page make sure that you use try/catch to handle them where they happens.
After some think maybe is not good practice to use it. Good practice is to use try/catch in the place that you may have throws and not a general one like that.
Last
You also get throw error here when the user close the connection before the end of the render, but if you log the errors you get the same on Application_Error - this is not a page error.
Exception of type 'System.Web.HttpUnhandledException' was thrown. --->
System.Web.HttpException: The remote host closed the connection.
The error code is 0x80072746.
In you Global.asax, handle Application_Error.
When a NullReferenceException is handled by the server a 500 response is created. Redirect all of your server 500 messages however you want. This guide will help.
Definitive Guide to Handling 500 Errors in IIS6, IIS7, ASP.NET MVC3 with Custom Page
You can hook up to every uncatched NullReference Exception, depending on what you want to do.
For instance you can use the global.asax, to be specific the Application_Error Event. You can get a reference to the exception, look for the type and perform a redirect there.
Another way to get ahold of exceptions would be to write your custom error provider, but that wouldn't give you the possibility to perform a redirect.
I am using ASP.Net 2.0. I found myself in an awkward situtation because I could not find the cause of an error. Up until now I have been using this idiom when it comes to accessing data.
try
{
access data
}
catch (SqlException exception)
{
Response.redirect("error.aspx");
}
finally
{
Dispose of connections, commands etc
}
Now I can never see what the actual error was because it is always handled. Sometimes I can run SQL Profiler and catch the last statement and run that in SQL Query Analyzer and see if there is a problem. That is obviously terrible.
So I thought that the global.asax Application_Error method would save me and I would email myself the exception. But this method seems to only be called for unhandled exceptions. So my question is, is rather better to not handle the exception at all, the system sends the email and use a customError page. Or is it better to ram the exception into the session, redirect to the error.aspx and try and do something with the error then. Is there a way to call Application_Error again? Because if I throw the exception again at the error.aspx then I get the yellow screen of death?
In my opinion, use a library (log4net for example) to log your exceptions and throw the exception again, let the asp.net redirect the error page to a custom page with web.config customErrors section.
Log4Net or Enterprise Library's Exception Handling Application Block both have email sending features.
Also take a look at ELMAH, very smart and pluggable exception handling module.
Logging would be invaluable here. In your catch blocks, log the error out to a log file. its a good idea to get in the habit of doing this at it can be a real life saver to see whats going on. Have a look at nlog which is a logging library. There are various tools out there too that allow you to analyse logs produced by nlog
Since you are using ASP.NET 2.0, your best bet is to do nothing.
ASP.NET added a feature called ASP.NET Health Monitoring. By default, this will log detailed exception information to the Application event log. It can be configured to send different kinds of problem to different destinations.
So, simply do nothing, and everything will be fine.
You can simply log the exception somewhere before redirecting to the Error page.
Something like :
try
{
//access data
}
catch (SqlException exception)
{
LogException(exception);
Response.redirect("error.aspx");
}
finally
{
//Dispose of connections, commands etc
}
Thus you can have it both ways, Customer will be directed to error page and still your exception is logged somewhere for you to review and get to the bottom of it.
By the way, there are many free logging libraries that you can use notably log4net and Enterprise library
In the Application_Error method in Global.asax I am trying to retrieve a value from session state.
I am able to access session state as long as I throw the exception. EG:
thow new Exception("Test exception");
However if it is an unhandled exception, i get the following error when trying to access session state: "Session state is not available in this context.".
Why the differences in behavior, is there a work around?
Thanks.
I hate ASP.NET sometimes...
So generating an error using:
Response.Redirect("thispagedoesnotexist.aspx", false);
The above line will redirect to Application_Error with session state not available
However
throw new Exception("test");
The above line will redirect to Application_Error with session state AVAILABLE
So instead of doing this all in Application_Error, in one spot, I will have to use try/catches through out my code to catch errors. Then gather data from session, log and email error details, then finally redirect to friendly error page. Lots of extra code..
Conclusion: Application_Error is worthless.
I think you are trying to access the session through HttpContext.Current.Session. I believe the difference in behavior is that in the unhanded exception handler, the request has gone into "Failsafe" mode and the page lifecycle (including loading and disposing the session) has finished.
Check out this page on the lifecycle for more info