I think this is trivial, but I cannot find the answer :(
I have a WP7 page that hosts some controls that I want to populate with date read from a web request.
The web request is done with:
WebClient wr = new WebClient();
wr.DownloadStringCompleted += new DownloadStringCompletedEventHandler(Event_DownloadStringCompleted);
wr.DownloadStringAsync(new Uri(theURL));
and this is called in the Page_Loaded event.
In Event_DownloadStringCompleted I try to assign the new values to the TextBlocks, that completely ignore this command.
What am I doing wrong? Do I need to find a different event to launch the web request? Or is it possible to "refresh" the page after the web request is completed?
Thanks
Your Event_DownloadStringCompleted is not called on the UI thread so it can't update the UI. Use the Dispatcher to get called back on the right thread. e.g.
page.Dispatcher.BeginInvoke(delegate() { textBlock.Text = "done!"; });
You might want to initiate the web request when the page's OnNavigatedTo() method is called, rather than when the page's Loaded event is fired, though I don't think this will solve your problem.
Are you sure that your handler of the DownloadStringCompleted event is called? If so, is the Error property of the DownloadStringCompletedEventArgs set to a non null value?
There are known display/refresh issues related to some display drivers introduced in the public beta. This has been known in some cases to be associated with ATI adapters. Some people report success following a driver update.
This may be affecting your refresh result.
Also you can check your driver is directx10 minimum and WDDM1.1 compliant per the WPDT system requirements. If not, driver upgrade (again), adapter change, or upgrade to Win7 if running Vista which has solved several obscure issues.
Also if you have the option, try running up your up on another PC with a different configuration.
Related
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?
Other than using a web service, is there anyway to call a method in a web app from a windows application? Both run on the same machine.
I basically want to schedule a job to run a windows app which updates some file (for a bayesian spam filter), then I want to notify the web app to reload that file.
I know this can be done in other ways but I'm curious to know whether it's possible anyway.
You can make your windows app connect to the web app and do a GET in a page that responds by reloading your file, I don't think it is strictly necessary to use a web service. This way you can also make it happen from a web browser.
A Web Service is the "right" way if you want them to communicate directly. However, I've found it easier in some situations to coordinate via database records. For example, my web app has bulk email capability. To make it work, the web app just leaves a database record behind specifying the email to be sent. The WinApp scans periodically for these records and, when it finds one with an "unprocessed" status, it takes the appropriate action. This works like a charm for me in a very high volume environment.
You cannot quite do this in the other direction only because web apps don't generally sit around in a timing loop (there are ways around this but they aren't worth the effort). Thus, you'll require some type of initiating action to let the web app know when to reload the file. To do this, you could use the following code to do a GET on a page:
WebRequest wrContent = WebRequest.Create("http://www.yourUrl.com/yourpage.aspx");
Stream objStream = wrContent.GetResponse().GetResponseStream();
// I don't think you'll need the stream Reader but I include it for completeness
StreamReader objStreamReader = new StreamReader(objStream);
You'll then reload the file in the PageLoad method whenever this page is opened.
How is the web application loading the file? If you were using a dependency on the Cache object, then simply updating the file will invalidate the Cache entry, causing your code to reload that entry when it is found to be null (or based on the "invalidated" event).
Otherwise, I don't know how you would notify the application to update the file.
An ASP.NET application only exists as an instance to serve a request. This is why web services are an easy way to handle this - the application has been instantiated to serve the service request. If you could be sure the instance existed and got a handle to it, you could use remoting. But without having a concrete handle to an instance of the application, you can't invoke the method directly.
There's plenty of other ways to communicate. You could use a database or some other kind of list which both applications poll and update periodically. There are plenty of asynchronous MQ solutions out there.
So you'll create a page in your webapp specifically for this purpose. Use a Get request and pass in a url parameter. Then in the page_load event check for this paremter. if it exists then do your processing. By passing in the parameter you'll prevent accidental page loads that will cause the file to be uploaded and processed when you don't want it to be.
From the windows app make the url Get request by using the .Net HttpWebRequest. Example here: http://www.codeproject.com/KB/webservices/HttpWebRequest_Response.aspx
I have an ASP.NET application that starts a long running operation during the Event Handler phase in the ASP.NET Page life cycle. This occurs when the end user pushes a button a bunch of queries are made to a database, a bunch of maps are generated, and then a movie is made from jpeg images of the maps. This process can take over a minute to complete.
Here's a link to the application
http://maxim.ucsd.edu/mapmaker/cbeo.aspx
I've tried using a thread from the threadpool, creating and launching my own thread and using AsyncCallback framework. The problem is that the new thread is run under a different userid. I assume the main thread is run under ASPNET, the new thread is run under AD\MAXIM$ where MAXIM is the hostname. I know this because there is an error when it tries to connect to the database.
Why is the new thread under a different userid?
If I can figure out the userid issue, what I'd like to do is check if the movie making process has finished by examining a Session variable in a Page_Load method, then add a link to the page to access the movie.
Does anyone have any good examples of using concurrency in a ASP.NET application that uses or creates threads in an EventHandler callback?
Thanks,
Matt
Did you read this?: http://msdn.microsoft.com/en-us/magazine/cc163725.aspx
Quoting one relevant portion from that link (you should read the whole thing):
A final point to keep in mind as you build asynchronous pages is that you should not launch asynchronous operations that borrow from the same thread pool that ASP.NET uses.
Not addressing the specific problem you asked about, but this is likely to come up soon:
At what point is this video used?
If it's displayed in the page or downloaded by the user, what does the generated html that the browser uses to get the video look like? The browser has to call that video somewhere using a separate http request, and you might do better by creating a separate http handler (*.ashx file) to handle that request, and just writing the url for that handler in your page.
If it's for storage or view elsewhere you should consider just saving the information needed to create the video at this point and deferring the actual work until the video is finally requested.
The problem is that the new thread is run under a different userid. I assume the main thread is run under ASPNET, the new thread is run under AD\MAXIM$ where MAXIM is the hostname.
ASPNET is a local account, when the request travels over a network it will use the computer's credentials (AD\MAXIM$).
What may be happening, is that you're running under impersonation in the request - and without in the ThreadPool. If that's the case, you might be able to store the current WindowsIdentity for the request, and then impersonate that identity in the ThreadPool.
Or, just let the ThreadPool hit the DB with Sql Authentication (username and password).
Everyone probably notices that most modern applications nowadays has a way for user to send crash/bug report either automatically or with user permission. Some examples are Mozilla Crash Reporter or most Microsoft applications.
I really like this feature since it allows me to collect the bugs report quickly with helpful information than just let my user reports the bug/issue traditionally such as submit a help ticket.
I wonder if there is an easy or systematic way to implement that capability in ASP.NET web application.
Have you guys had any experience or knowledge to share for both WebForms and MVC applications? Or if this could be implemented in Client-side like JavaScript/JQuery, that'd be good.
Thanks!
ASP.NET 2.0 introducted Health monitoring, which allows you to do this by just adding some stuff to the web.config. See: http://msdn.microsoft.com/en-us/library/ms998306.aspx
It can log to mail, sql, eventlog, etc. and allows you to set buffers. So it for example won't kill your mailserver if the sql database goes down or if some user discovers a bug and tries to call it too often a second :-)
You can also log failed authentication and app pool restarts with it, it's pretty usefull if you just need it working quick. It's still questionnable if it is the best solution to manage all the errors. Because it might not got all the information you need, for example browser version or smt like that.
ELMAH is a library that plugs in and detects exceptions. You can also log an event yourself. The events and a great deal of data like url parameters and browser information can be emailed to administrators and optionally stored in a database for display. (Rather like an event log for the web site.) It doesn't have a built-in user form that I've seen, but can probably be extended to include such an option.
I've been using/customizing it for about two years now and it is really exceptional.
Another option might be to use Kampyle which includes a feedback box on the bottom right of your web site. You could use Javascript to trigger the box to appear if an issue is detected on the web site.
For an ASP.NET applicatino--or any Web application for that matter--isn't this just a two-step process of:
Logging the error (obviously); and
Put a form on the error document to allow the user to enter feedback.
Or is there more to this?
Your errors will pass through the Application_Error method of the Global.asax.cs file (which you may have to create). I use this fact to capture the error and log it to a database:
void Application_Error(object sender, EventArgs e)
{
try
{
SqlConnection errConnection = new SqlConnection("Your connection string");
// After setting up a command object, I call a stored procedure to save information about
// the crash. I pass two primary arguments. The first is the URL:
errCommand.Parameters.Add("#URL", SqlDbType.VarChar).Value = Request.Url.ToString();
// The second is the error information.
errCommand.Parameters.Add("#EI", SqlDbType.Text).Value = Server.GetLastError().ToString();
// I pass some other information from my session as well...
// After setting up an output parameter called ErrorID, I call the command...
errCommand.ExecuteNonQuery();
// Now Error ID is stored in the session.
Session["ErrorID"] = (int)ErrorID.Value;
}
catch { } // I do NOT want the error handling call to throw an error.
}
Now, you should have set up your Web.Config file so that a specific page gains control when an error occurs. In this page, you'll check the session for the error ID and show it to the user. In the output, I ask the user to write down the error if they would like to call us for more information. If we do receive a request, I can go into the database and get a complete trace of the error.
You can checkout my tutorial on how to implement exception logging in asp.net - http://jesal.us/blog/index.php/2008/04/08/exception-logging-using-the-database/
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.