I'm experiencing some problems with the use of System.Web.Caching.Cache.
Basically I'm using
Cache.Insert(tablename, newlist, null,
System.Web.Caching.Cache.NoAbsoluteExpiration,
System.Web.Caching.Cache.NoSlidingExpiration);
to insert objects into the cache, and Cache[tablename] to retrieve them on a webform.
What I'm experiencing is that if I refresh the browser that calls these methods, then the data is there, and Cache.Count reflects this.
However, if I close the browser and start it up again, or start a different browser on my test machine or another, then the Cached data is not there.
Ie the Cache is working as if I was using the Session Store. I've also tried using the Application store too, but with exactly the same results.
I've had a look through my application pool settings and web.config, and can't see anything obvious.
Any help with this would be much appreciated, as requerying the databases to get the information to put in the cache would slow down the webform a great deal.
I'm not sure I'm being clear enough.
To reproduce.
browser 1 opens webpage, no cached data
browser 1 refreshes webpage, cached data
browser 2 opens webpage, no cached data
browser 2 refreshes webpage, cached data
browser 1 refreshes webpage, cached data
So as you can see, it's working exactly as if it was session only data, not a common cache. Using the callback probably wouldn't tell me anything, as the data is still there, just not available to a fresh session
Sounds like you restart the application by pressing F5 in Visual Studio.
Just open a new browser Window without restarting the application.
Related
I have an ASP.NET 4.5 web form running C# code behind on a server. A specific form often takes some time to finish while it updates and changes various database records. However, if the user closes the tab or tries to reopen the web form, it will try to check the users status in the database and fail when those later change due to the first running process.
The need is to track this specific instance of the process and user, and if it is still running, prevent the page from loading fully or redirect. I was hoping to find and store some user and process information on a cookie and then simply check for this each time on page_load. I was not able to find these variables/properties.
Am I going about this the right way, and if so, how can I accomplish this?
Thanks!
I was not able to find the exact solution I was looking for. At the moment, I cannot see any way to find a server side identification id of the process.
Instead, I referenced How to tell if a page unload in ASP is a PostBack and made it so that the page would warn when being unloaded before the confirmation screen is shown. As long as the form opens to the same named tab, the user would be given the warning screen and given a confirmation before they could close or reload a new web form instance.
We have an ASP.NET 3.5 application which we have created for a logistics company, which allows their customers to input deliveries/jobs and get them onto the system.
The core page in the system is the Add Job screen as as you can imagine - as the user builds up their job, we store some information of this in the Session. Then when they commit the job, or in the Page_Load event when the request is not a postback, the session is cleared ready for the next job.
We are having an issue with a small percentage of the customers, in which the users sessions appear to be being wiped before the commit happens - the users have assured us they are not trying to use multiple sessions (i.e. 2 windows of the same page). We put in some error trapping that logged whenever the sessions were cleared on that page, and it seems that 'clear session' in the Page_Load event is firing a few seconds before they click submit. Please note we have a lot of autopostback controls on this page.
Are there any ASP.NET quirks, or browser quirks for that matter, that will mean the IsPostback property will incorrectly be false? This is a very sporadic issue and we are having no luck in replicating this!
As adviced by many comments the session IS the wrong solution. It could be reset by a lot of things (app pool recycling for example).
You should not force the user not to use different browsers or tabs, so the right choice is move data to ViewState/Control state.
If for some weird reason you still have to keep data in the session consider switching to a persistant session storage (i.e. using sql Server).
I have a problem with Internet Explorer and cache (I think).
Easy explained, I'm trying to edit a user in my SQL database using LINQ-to-SQL, which works perfectly.
After the user is edited, it sends me back to a page I've made with a list of all users, and I can then click on any user I want to edit.
The problem is, if I then click on the same user I just edited, the changes haven't been done, but in the database, they have been changed, so I think there might be a problem with the IE cache or something.
Anyone knows if there is a way in Visual Studio to clear the IE cache for this specific page?
I know I can just press ctrl+F5, but I want it to update without having to press ctrl+F5.
Btw, my website is programmed in c# and .net 4.0.
You probably need to refresh your data context.
L2S doesn't 'cache', as such, but it sometimes needs prompting to refresh the data from the database, depending on how you've done your data update.
You can try appending random number in the link of the user, like:
<a href="Page.aspx?userId=123&rnd={JUST A RANDOM NUMBER OR TICKS} />
This concept is the same as the JavaScript being cached, in the IIS it will have the same interpretation but will force to get the new one.
I have recently rolled out a new ASP .Net application. This application uses .Net 4.0 and the Entity Framework 4. It is a "basic" CRUD application. I almost exclusively used the EntityDataSource for Data Access.
The users have reported "ocassional freezing" of the application (they all use IE 8). If the user closes his browser and starts back up, the app is fine. It happens maybe once or twice per day total, usually to the heavy users. (So, I have been leaning toward memory leack or some other kind of resource limitation.)
Until just a little while ago, I have never seen this happen. It dosn't leave anything in the Event Log on the client PC nor Server. Also, there is nothing in the IIS error logs or the SQL logs.
A little while ago, I finally got it to happen. I was switching all of my EntityDataSources to use a single Object Context per page. I downloaded the EF Profiler (which seems to be a great product) and it pointed out that I am using multiple object contexts on many of my pages, due to the fact that many of them have more than one EntityDataSource. So, I was cleaning all this up and testing each page, when lo and behold....IE stopped loading pages!
At first, the page started loading slowly (and this was a page that I had already modified to use a single Object Context, so although I still believe I need to implement this "singleton" pattern throughout all my pages, I guess it isn't the culprit! Anyway..), then at some point I received:
Message: Sys.WebForms.PageRequestManagerTimeoutException: The server request timed out.
Still, nothing in the Event Log. I also checked the IIS web logs and I don't see anything, but they are pretty tough to read with the naked eye, I may have to download a parser to make sure there is nothing in there.
Anyway, I decided to start up another window and navigate to my app, and sure enough that window worked fine, no problems. I went back to the windows that stopped responding, refreshed it, waited... went to the home page of my app (which is basically just some static html.. and nothing.. ). Next, I opened a new tab in the window that is currently frozen and that tab works fine. So, I go back to the window that can no longer load pages from my app and try some other web sites.... espn.com loads fine, msn.com loads fine, I then enter the URL for my app home page (and tried some other pages in my app) and NOTHING. IIS doesn't even log the attempts in its Log Files (its like IE has just decided not to do anymore "gets" for my localhost!). Finally, after waiting for a while (while I was typing this post) I now have this error message in that window:
Internet Explorer cannot display the webpage. What you can try: The problem can be caused by a variety of issues, including: BLAH BLAH BLAH...
So, I jump back to that window and it can still browse Internet sites just fine. But, once again when I try to go to any of the pages in my app, I get NOTHING (spinning blue circle in the tab). So, once again I start a new tab in that same browser and I can browse around my application just fine.
What has my app done to this browser instance that will no longer let it load any of its pages (in fact, it seems like it isn't even doing a GET on any of the apps pages, since there is nothing new in the IIS logs...except for when I load the pages in these other tabs and/or browser windows that work fine, so the logging is still working...)? I will be forever indebted to the person that can help me figure this out. I am not sure it will do much good, but I am going to leave this browser window up on the chance that someone can tell me some things to try to diagnose this problem. It feel like I am THIS close to figuring it out. I finally have a window up that is misbehaving. I am afraid to close the window or do a new build on the app until I get some good input on things to try....
I should add that when this happened to me, I was running on my local PC, so I was the only user and only had one window open to the app..
Although, I am completely stumped!
We had the same issue and seemed to fix it by adding the following JavaScript to all pages with ajax:
window.onunload = abortRequest;
function abortRequest() {
Sys.WebForms.PageRequestManager.getInstance().abortPostBack();
}
I hope this helps!
sounds like a request just takes too long to execute. A web-browser is only allowed to keep two concurrent connections to a single webserver unless you utilize http pipelining (which isn't well supported anyway). However, My experience is that this is per browser, not per tab.
This is why nothing shows up in your logs, because your browser never initiate a request because it is waiting for the page to finish loading before it can fetch another page. I would start looking into the last request initiated before the lockup, it is probably that page that locks for some reason and never finishes.
ASP.NET utilizes only one thread as long as all request are sequential. As soon as you fire up two request simultaneously, a new thread is initiated (Init() on HttpApplication is invoked), and that can cause intermittent errors if you do funky stuff on Init().
If you think this is related to EF, you might read up on how to avoid locking in multi-threaded environment (because a web application is very much multi-threaded however this usually kicks in a production environment).
Ugh, I feel your pain - I hate these types of issues. Here's my divide-n-conquer process when something like this is happening (adapted somewhat to your case):
Step 1 - Environment Visibility
Get yourself set up so you can roughly see inside your systems. Set up Performance Monitor, and add a couple of important counters (IIS Current Requests, ASP.NET Current Requests, SQL Server - Active Transactions). The idea here with the "active requests/transactions" counters is you want to find out which part of the system is holding on to the request.
Additionally, add counters for total request time in IIS and the DB (so you can see it climbing as something is hanging on).
On your client PC, set up Fiddler.
Step 2 - Reproduce Issue
Usually at this point, the application realizes you can see it and starts behaving perfectly. ;) Stop and make sure you can still reproduce the issue.
Step 3 - Take the DB out of the equation
Create 4 pages in your application:
Static HTML file (.htm) that will NOT go through the ASP.NET runtime engine. This is your baseline for raw IIS.
ASPX page with no tricks (no database access, no processing, just a simple page that ASP.NET can spit out)
ASPX page with one simple database call (of some size, maybe do a single big query or something)
ASPX page with some complex transactions (multiple queries, etc)
Step 4 - Reproduce and measure
Since this issue will probably be pretty obvious once you can see it, find the bottleneck with your performance counters and Fiddler. Your issue sounds like you could have an intermittent connectivity issue (either between client and web server or web server/SQL), especially if IE is giving you the "page cannot be displayed" error, but you should see that in Fiddler. On the server side, you should see one of those performance counters hanging.
well, sounds like the app is waiting for a database operation to complete but is locked, probably because of another operation.
Try using the SQL profiler to trace the activity, and isolate what processes are running for a long time.
You can differentiate the requests using the SPID column in the trace view, it contains a unique ID number for each session from your App.
I have new information regarding this issue.
The application uses Integrated Authentication. This causes every reqest to come back (twice) with access denied, before IE send the credentials.
I can't help but wonder if this is what could be causing the "time outs".
I implemented an Ajax "Loading" animation on every page that prevents the user from clicking a button until the previous request is completed and that has GREATLY diminished the amount of "freezes" the users are experiencing.
Although, it still happens somewhat often.
Many of our users, internal and external, start our web application. Then at some later point, they open a new window from within the browser. They want to have 2 independent sessions of the application running. However, by doing it this way they are actually using the same session data.
Is there a way, in code, to determine if there is another browser window open with the same session?
We're using VS 2008, C# and/or VB.Net.
Thanks.
COMBINING MY RESPONSES FROM BELOW:
Maybe I'm saying this wrong. When they open a second window and change it to a different widget number, and then go back to the original window, on the next post-back it will be using the second window's widget number, not its own
We are using IE7.
The major browsers that I've tested apps on (IE, FF and Google Chrome) all default to using the same collection of cookies regardless of whether you are opening a duplicate web page in a new tab or a new browser instance.
The result is that 2 different tabs, or 2 instances of the same browser, by default, will look like the same session to the server.
Because the multiple instances use the same cookies, the server cannot tell requests from them apart, and will associate them with the same Session data, because they all have the same SessionID, assuming cookie-based SessionID.
Generally there is nothing wrong with this behaviour, and you would have to have a good business case against that behaviour to want to code a work around.
I do not believe it is possible to distinguish the different browser tabs from server side code. There may be some sort of client side script hack that would help.
Would it help to include a Html meta refresh tag so that the various tabs at least update themselves periodically?
If, on the other hand, what you are after is to treat a group of user/server interactions as a kind of "session within a session", you may be able to do this by storing a random Guid (or Widget Number) in ViewState, and checking it on postback.
Hope this helps.
IE8 - shares session between tabs and browser instances; new session can be started using File->New Session command
IE7 - shares session between tabs but not between browser instances
Firefox - shares session between tabs and instances; another Firefox can be started in different profile (firefox.exe -P "profileName" -no-remote) and then have separate session
See http://blogs.msdn.com/ie/archive/2009/05/06/session-cookies-sessionstorage-and-ie8.aspx for discussion of this topic for IE7 and IE8.
They're not sharing the same data. A new session is started in the new browser window and a separate trip to the database is initiated.
You can inspect the headers in Fiddler or you can output the Session.ID in the Windows. Sessions are created for each browser instance, not each window.