I am using the following code to capture exceptions in the application, and save them in the Session object. The exception is then retrieved from Session in the error handler page to which the app automatically redirects:
protected virtual void Application_Error(Object sender, EventArgs e)
{
try
{
Exception ex = Server.GetLastError();
Session["exception"] = ex;
}
catch { }
}
I have one problem with this code:
Session is not available if a malformed path gets in: "example.com/"foo" - Exception is thrown when accessing it, and NULL is retrieved from Session object in the error page
What is a better way to save exception information in the application and pass it to the error handler action?
If you are trying to log exceptions then take a look at the elmah project.
Scott Hanselman has a good introduction
If you can't use ELMAH for any reason,
http://www.genericerror.com/blog/2009/01/27/ASPNetMVCCustomErrorPages.aspx
Related
I saw similar post Error Handling with WCF Service and Client Application to my question but I needed more help.
I have a MVC project with the WCF Service. I understand that WCF needs to throw a FaultException. But my question is what is the best way to show the error message created by an error in WCF. I just want to redirect all the errors (possibly all FaultException) to one error page (will be generic) but message will be different.
I also would like to use [HandleError] attribute so that I don't have to implement catching FaultException for all the methods calling the WCF service.
As you know how you can handle WCF exceptions but in my opinion this is better to observe these:
1-This not good idea to show user exactly exception message, this is better to show very understandable message for example "Operation get failed there is may problem with back-end service, try again or notify admin"
2- It's is boring end user to redirect to public error page.
3- This is better show the public prompt to user which tell user that the operation get failed exactly where the user do action not redirect it to another page.
4- At the end If you want to do what you want try these:
try
{
//Call your wcf
}
catch(Exception exp)
{
//Logging.Log(LoggingMode.Error, "You message , EXP:{0}...", exp.ToString());
Response.Redirect("~/ErrorPages/Oops.aspx?Error=WCfOperationFailed", false);
}
in your error page page_load:
switch (Request.QueryString["Error"].ToString())
{
case "WCfOperationFailed":
litError.Text = string.Format("<h2>Error!.</h2><br/><p>{0}.</p>",GetError());
break;
default:
break;
}
public string GetError()
{
Exception lastError = Server.GetLastError();
return lastError.ToString();
}
or you can redirect error message as a QueryString to error page and show it to user in Page_load like:
//in catch block
Response.Redirect("~/ErrorPages/Oops.aspx?Error="+exp.Message, false);
in error page Page_load :
txtError.Text = Request.QueryString["Error"].ToString();
However, you can trap errors that occur anywhere in your application by adding code to the Application_Error handler in the Global.asax file:
void Application_Error(object sender, EventArgs e)
{
Exception exc = Server.GetLastError();
if (exc is HttpUnhandledException)
{
// Pass the error on to the error page.
Server.Transfer("ErrorPage.aspx?Error="+exc.Message, true);
}
}
This link can be helpful there are some examples
Error Handling
I have this simple controller, whose Get method is called with ajax to look up zipcodes via an Entity Framework repository.
[Authorize]
public class ZipCodesApiController : AppApiController
{
public ZipCode Get(string zipCode)
{
return unitOfWork.ZipCodeRepository
.Get(x => x.Zip == zipCode)
.FirstOrDefault();
}
}
In production, my logs show that System.OperationCanceledException: The operation was canceled. is thrown quite often. I think what's going on is that users are viewing an address detail page, but navigating away or closing their browser before the ajax zipcode lookup returns. I guess IIS is telling my controller that they are no longer connected, and the .NET framework throws an exception?
This seems harmless, but it also seems like a bad idea to wrap the call to ZipCodeRepository in a try and have an empty OperationCanceledException catch clause.
I've googled the error and it seems to come up quite a bit in parallel programming, which is not something I am particularly familiar with.
What is an appropriate way to handle this exception? I think it's safe to ignore, but am I wrong about that, and the Entity Framework should be alerted so that it can clean something up (my AppApiController does have a dispose method at least)?
I get the same exceptions in my web API application, however i can catch them with the Application_Error method in Global.asax.cs
protected void Application_Error(object sender, EventArgs e)
{
Exception exception = Server.GetLastError();
Response.Clear();
OperationCanceledException httpException = exception as OperationCanceledException;
if (httpException != null)
{
var token = httpException.CancellationToken;
if (token.IsCancellationRequested)
{
// clear error on server
Server.ClearError();
Request.Abort();
}
}
}
I don't know if that is right.
I am initializing FluentNHibernate from Application_Start event like so:
Fluently.Configure()
.Database(OracleDataClientConfiguration.Oracle10
.Driver<NHibernate.Driver.OracleDataClientDriver>()
.ConnectionString("MyConnectionString")
.DefaultSchema("MySchema")
)
.Mappings(m => m.FluentMappings.AddFromAssemblyOf<SomeClass>())
.BuildConfiguration()
.BuildSessionFactory();
If the connection string is bad, or connection to the DB fails for some other reason, I get a TNS No listener exception. I would like to display/log this exception but Application_Start (and Applicaiton_Error) doesn't have an HttpContext or Response object in IIS7 Integrated mode. The user gets a yellow screen of death telling them to turn custom errors On. Elmah doesn't log the message either. I would like to solve the problem in one of two possible ways:
Disable nhibernate configuration from connecting to the database on configuration.
Provide custom user feedback based on the error and get Elmah working (somehow). This would be my ideal choice.
I was able to move NHibernate configuration to run on Session_Start, as described here, which gets exception handling working for this error, but then I get other exceptions that can be misleading to the root cause of the problem. Does anyone have a good solution for this scenario?
Thank you.
This is what I do:
void Application_Start() {
try {
// setup your app / nhibernate
} catch(Exception ex) {
Application["StartupError"] = ex
}
}
void Application_BeginRequest() {
var startupError = Application["StartupError"] as Exception;
if (startupError != null)
throw new Exception("Error starting application", startupError);
}
In your BeginRequest method you have access to the Request and can do what you want to show the error (or show a nice page)
While debugging my MVC 4 application in VS2010 SP1, the Application_Error() handler was invoked but Server.GetLastError() was null.
protected void Application_Error()
{
var exception = Server.GetLastError();
// exception is null. How is that possible?
}
MSDN states Application_Error is
called if an unhandled exception occurs anywhere in your ... application... You can get information about the most recent error from the GetLastError method.
The MSDN docs for Server.GetLastError() states
Return value: The previous exception that was thrown.
How can I possibly be in a state where Application_Error() was called but Server.GetLastError() returns null?
Are you using custom error handling in your web.config? I believe that if the browser issues a redirect, the previous exception will be lost. Take a look at this answer and see if your situation is similar.
I have mvc 3 application which when a Standard generic throw new Exception is thrown in code the error page from Views\Shared\error.cshtml is shown. This is done by simply setting <customErrors mode="On"/>. (This is As expected and as Desired)
The application is using WCF services in middle tier which when these services generate FaultException MVC is not showing up the error page it is showing details of the web service call to the user on screen. All I want to do is handle the error in my code and show the user the Error.cshtml. I have tried changing global asax but this dosent work.
protected void Application_Error(object sender, EventArgs e)
{
Exception exception = Server.GetLastError();
if (exception.GetType() == typeof(FaultException))
{
throw new Exception("There was a fault exception that i do not want to show details of to user.");
}
}
Try creating an ErrorController as asp.net MVC will try to resolve the link you specified in the web.config as {Controller}/{View} unless you specify it to ignore that page. Also, you may want to apply an attribute to handle exceptions instead.
You can also create a error controller/view and in your catch block redirect to the custom error page of your choosing
try
{
foo.bar()
}
catch(SpecificException)
{
RedirectToAction("500", "Error");
}