How to kill a javascript async call to a .net webservice? - asp.net

My javascript code is calling a asp.net webservice, so i have a call to the webservice something like this:
MyWebservice.GetData(param, ResponseReceived, ResponseTimeOut, ResponseError);
When the webservice returns data, ResponseReceived method is called.
However sometimes the user might navigate to another url before the webservice call actually returns, in such a scenario FireFox throws an Error saying 'An error occured oricessubg the request. The server method GetData failed'
So my question is how can i kill the async call when the user navigates to another page or makes another request to the webservice? I know in a normal XMLHttpRequest i could have called Abort method, but not sure how to make it work with the above webservice proxy.

A good practice would be to keep your common functions in a common place, which is accessible from all of your pages.
This would include the OnError function. That way you can safely reference that same function from all of your pages. If you need to provide custom Error Functionality, you can either override this function on your page, or include a handler in your common function, and call if it was assigned.
A good place to put such common function would be inside a root master page, or a shared JavaScript file referenced from root master page.
What is good about this, is that hopefully your OnError function does some logging, so you can get an idea of what fails and how often so that you can design your app accordingly.

Ok I figured out a solution, I can call get_executor() method to get an instance of the XmlHttpExecutor class, on which I can call the abort method. Hope it helps others facing a similar problem.
I'm still eager to find out other solutions.

Related

Webmethod authentication not passed

I'm new to this AJAX approach when you're not supposed to use UpdatePanel but rather go with WebMethods and WebServices. My main problem is authentication.
When page is entered or postback request is created, everything works fine. Authentication is passed correctly and I can access Thread.CurrentPrincipal.Identity and get my user identity object from there.
However this changes when I try to call WebMethod on my page. Call is passed correctly to server and everything seems to work just fine until i try to get user identity from thread. Then I get just Anonymous user instead of real one. Enabling session on webmethod didn't seem to help much.
Any ideas what might cause this problem and how to solve it? Someone mentioned that authentication cookie needs to be passed along with the request, but how am I supposed to do it?
Any help will be appreciated.
Edit:
Some clarification and code:
My application is written in standard asp.net. After some deeper research in legacy code I've found out, that all authentications are done in some base class from wchich all other pages inherit. Each time page is loaded, user principal are obtained from HttpContext.Current.Session("..."). I think this is far from good solution, but I'll need to stick with it right now. Problem was, WebMethod is not firing whole page lifecycle since it's static. I've fixed it right now by calling method that obtains user data from session.
I would like to get some ideas how this could be created correctly and what problems might be result of session based authentication.
PageMethods.SomeMethod(parameter, SuccessDelegate, FailureDelegate);
This is how I'm calling WebMethods right now. I assume it's passing all required cookies, am I right?
It depends on how you're calling the method and in what manner?
Jquery for instance with its Post method should push all cookies (including your FormsAuth / Session cookie) up with the request that should still authenticate as appropriate. Bare metal techniques might be making lightweight calls that simply do not push the cookie up...One way to monitor this is by using Fiddler to observe the request and a browser based development plugin like Firebug and see what is occuring and amend your JS code as appropriate.
Personally, if you are starting a brand new project and there is no pressing need to expose your services beyond your web application then I would suggest looking at ASP.NET MVC where you can make Jquery / client-side up to the controller and get your authentication wrapped up for free. I've recently created something simliar using WCF JSON endpoints and some inevitable pain, I then saw MVC and kinda kicked myself...
As noted in comment above, the issue lies in legacy code that handles users. It is needed to make call to special function that assigns appropriate user data to handling thread. Not a best solution, but that's how it sometimes is with legacy code. What you gonna do?

Server-side ASP.Net Ajax exception handling

I am using ASP.net's AJAX framework and I am trying to do some exception logging on the javascript-called webservice.
Looking through the web, I find some people handling them client-side and sending them back to the server. I'd prefer not doing that since it relies on an other server call (if it failed the first time, sending an other request doesn't look like a good idea and that makes me change all my calls)
I see some other people decorating all their methods with try... catch blocks (which leads to duplicate error handling, and yet an other try catch block).
However, I'm trying to achieve something similar to global.asax's Application_Error() which handles every uncaught exception (nope, it doesn't seem to be called for AJAX called methods exceptions).
Is that even possible?
Use ELMAH - it can capture ajax errors.

Unable to send mail asynchronously

I'm using a separate class and unique method for sending mail.All my web pages, will call the method to send the mail. But, I'm using Client.SendAsync() to send the mail. The following error occurs while sending the mail asynchronously.
"Asynchronous operations are not allowed in this context. Page starting an asynchronous operation has to have the Async attribute set to true and an asynchronous operation can only be started on a page prior to PreRenderComplete event"
I set Async=true in #page directive, but, as I'm using separate class, so no use of it. Is there any other way to overcome this problem?
Seems you just need to start your async task before PreRenderComplete event; do you mind to post some relevant ASP.NET code?
Also, read this: Running an asynchronous operation triggered by an ASP.NET web page request
This article may be of some help to you:
Fire and Forget Email, Webservices and More in ASP.NET
Setting Async to true is OK if that separated class is declared, instantiated and within the context of the page request.
However you probably need to handle SendCompleted event.
See the sample codes in this MSDN Reference.

Extend the exception thrown from ASP.NET when calling a Webservice from JQuery

I'm using JQuery to load controls dynamically in an ASP.NET development environment using JSON and WebServices. Within this solution I have a business logic layer which has a built in validation mechanism (i.e. validating properties and business rules similar to that of CSLA)
When requesting a new control to be loaded dynamically using JQuery and an ASP.NET WebService, I would like to validate the input from the current control against the business logic validation mechanism (i.e. server side validation) and notify the user if there was any problems.
I managed to achieve this, however, when validation fails in the web service I would like to throw a customer exception containing the validation field id's and associated error messages.
In JQuery, I test for this specific ExceptionType and would like to apply the error messages dynamically to the controls listed in the exception type properties. This is where my problem comes in. Even though I created a custom exception with custom properties the exception that is passed to JQuery in JSON format from the WebService is still a standard exception with none of the additional properties listed. I could simply create a JSON formatted string of values in the exception's message property but would ultimately prefer something a little more elegant. Does anyone know how you can override the serialized exception created by ASP.NET for situations such as this...
Thank you in advance...
G
I ran into something very similar a couple days ago - basically there's no way to make ASP.NET generate custom exceptions. This is by design, since returning a specific type of exceptions would
[...] expose implementation
details/bugs to the clients. We could
do something with special exception
type that we let pass through, but its
too late for this release [...]
You could always return different HTTP status codes, and have the browser handle them as custom exceptions - for example, a 500 error would mean one thing, a 401 something else, etc. I think the best solution is to make your method return a string with the exception stack - not elegant, but at least this way the client has all the exception details.
Dave Ward also has info on ASP.NET AJAX service errors.

Using EndRequest Event to close NHibernate Session with IIS 7

I am using NHibernate on a new ASP.NET project, and am running into what I believe to be strange behavior. I am attempting to manage my session by using an HttpModule to catch the EndRequest event and close the session. This is working fine, however, after the EndRequest event fires, I am getting an exception in the OnLoad event of one of my custom controls that is attempting to read a Property from my object that is lazy loaded. I get an exception stating 'failed to lazily initialize a collection, no session or session was closed'. Turning lazy load off for these properties does fix the problem, and is an acceptable solution. But this seems to be going against what I always thought to be true.
I would assume that the OnLoad event and all server side processing would be done at the point that EndRequest is fired. This is also the first time that I have used IIS 7 on a project. Is this a reason for the behavior? What is the expected behavior?
I just had a 'palm slaps forehead' moment. Despite the fact that I am in fact deploying to an IIS 7 server, I have been debugging using the VS 2008 Built in Web server (Casini). Casini passes all requests through the ASP.NET pipeline, IIS does not. This was causing a request for an image file or javascript file (or any other static resource) to close my NHibernate session before I was actually thinking it should close.
Thanks for the list of resources, I will certainly look into them.
If your object is lazy-init and no session is open, resolving the properties will fail.
Remember that lazy exceptions will most probably appear when you have some relationship with another entity that hasn't been initialized.
http://forum.springframework.org/showthread.php?t=13474
I would also recommend using something like the HTTP Module in Rhino Commons to manage your NHibernate Sessions.
You should use a shrinkwrapped package for dealing with this.
I like to use Autofac with ASP.NET/MVC integration. You simply ask the RequestContainer for an ISession whenever you need it and, because the ISession is IDisposable, the RequestContainer automatically knows to dispose of the ISession when the current request ends. Everything is taken care of for you.
use HttpModule if you need lazy loading. Inherit your class from it and then you'd have two methods you can override (can't remember their names). First one is called each time any page is requested. Open the session there and put the session in viewstate. The other method is called when page is posted back, close your session there.

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