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• Network Load Balancing (NLB): is it suitable for "stateful" ASP.NET applications?

  - by micha12

  Hi everybody, I have posted the following question concerning ASP.NET web farms. http://stackoverflow.com/questions/1816756/how-to-create-an-asp-net-web-farm/ Guys recommended using Network Load Balancing (NLB) as a primary way of creating a web farm. However, Wikipedia says that "NLBS is intended for ... stateless applications". Our web application, however, is absolutely "stateful": it is a closed site to which users will have access by login and password, and information for every user will be different: people will see their own trades and operations. Should we still use NLB in this scenario? Thank you.

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• Facebook - using an external flash application to connect via PHP

  - by Anonymous

  So, I have this application that needs to connect to facebook. It uses php for all of its data access, in older examples of the facebook API, i see people get the UID, and sessionkey from the iframe page, then send them to php and run a function called $facebook-setUser($UID, $sessionKey). This is how the majority of the tutorials online are doing it. That would be great, except the newest facebook API doesn't have any function like that. I have been scouring the web for 2 hours and have found nothing relating to the disappearance of this seemingly critical function. So, I have a flash application that needs to authenticate via a stateless php resource. I would love it if my PHP code could be completely uncaring if the request originated from flash, or iphone, or another application altogether-it should just need userId and and sessionKey. Is this still possible? Thank you in advance for your help! :)

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• What is the difference between MVC model 1 and model 2?

  - by Alex Ciminian

  I've recently discovered that MVC is supposed to have two different flavors, model one and model two. I'm supposed to give a presentation on MVC1 and I was instructed that "it's not the web based version, that is refered to as MVC2". As the presentations are about design patterns in general, I doubt that this separation is related to Java (I found some info on Sun's site, but it seemed far off) or ASP. I have a pretty good understanding of what MVC is and I've used several (web) frameworks that enforce it, but this terminology is new to me. How is the web-based version different from other MVC (I'm guessing GUI) implementations? Does it have something to do with the stateless nature of HTTP? Thanks, Alex

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• EJB3.1 Remote invocation - is it distributed automatically? is it expensive?

  - by Hank

  I'm building a JEE6 application with performance and scalability in the forefront of my mind. Business logic and JPA2-facade is held in stateless session beans (EJB3.1). As of right now, the SLSBs implement only @Remote-interfaces. When a bean needs to access another bean, it does so via RMI. My reasoning behind this is the assumption that, once the application runs on a bunch of clustered application servers, the RMI-part allows the execution to be distributed across the whole cluster automagically. Is that a correct assumption? I'm fine with dealing with the downsides of that (objects lose entityManager session, pass-by-value), at least I think so. But I am wondering if constant remote invocation isn't adding more load then necessary.

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• Web services Authentication Jungle

  - by redben

  I have been doing some research lately about best approaches to authenticating web services calls (REST SOAP or whatever). But none of the Approaches convinced me... But i still can't a make a choise... Some talk about SSL and http basic authentication -login/password- which just seems weird for a machine (i mean having to assign a login/password to a machine, or is it not ?). Some others say API keys (seems like these scheme is more used for tracking and not realy for securing). Some say tokens (like session IDs) but shouldn't we stay stateless (especially if in REST style) ? In my use case, when a remote app is calling one of our web services, i have to authenticate the calling application obviously, and the call must - if applicable - tell me which user it impersonates so i can deal with authorization later. Any thoughts ?

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• simple EJB jar deployed in jboss with its own log4j configuration

  - by user309281

  Hi All I have a simple EJB jar with a stateless session bean, deployed in JBOSS AS 4.2.2, unde r/server/default/deploy. The bean is registered under JNDI tree as viewed from jboss jmx console and I am able to access it through a remote java client outside JBOSS. Inside EJB jar, I have added some logging to be written to a separate log file, using apache log4j jar and log4j.xml. But I am not able to view any of the logs. Also I do not wish to use jboss-log4j.xml, since there will be many other EJBs to be deployed and wish to have separate log4j for each EJB application. Here is my one of the EJB-jar contents: EJB_DS.jar: log4j.xml classes apache log4j jar is added to /server/default/lib path. Kindly highlight if i have missed any points for enabling log4j configuration With Regards, Krishna

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• TCP Server to push data to a Web Browser

  - by isurulucky

  Hi, I have a TCP server, which is connected to a web page via a Web browser. It is easy to send a request to the TCP server by the web page via the Web Browser, but is there a way that TCP server can push data to the web browser, without waiting for a request from browser side?? My initial idea was that this is impossible, since a browser is stateless. But I was told there are ways to do that... Any ideas? Thank You!!

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• @Local annotation in EJB 3.

  - by stratwine

  Hi, I have a stateless session bean and a standalone-java-program acting as a client. The bean method executes just fine when the interface is marked @Remote. However,when I mark that interface with @Local instead of @Remote, I get the following Exception. [java] javax.naming.NamingException: Could not dereference object [Root exception is java.lang.RuntimeException: Could not find InvokerLocator URL at JNDIaddress "chapter1/HelloUserBean/local"; looking up local Proxy from Remote JVM?] But I expected even the latter to work, since it is the same computer that the code executes in. Seeing this behavior, I am assuming that, the Application-Server and the Standalone-Java-Program use different JVM instances and not a single JVM instance and so this client can access only through a remote interface. Is that assumption correct ? Thanks !

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• Algorithm for redirecting the traffic

  - by TechGeeky

  I was going through the interview questions and found out the below question which I am not able to answer it. Can anyone provide some sort of algorithm for this problem how can I solve it? There are a cluster of stateless servers all serving the same pages. The servers are hosting 5 web pages- p1.html, p2.html, p3.html, p4.html and p5.html p1.html just redirects users to the other 4 pages Requests to p1.html should result in 10% of users being redirected to p2.html, 5% of users redirected to p3.html, 20% of users redirected to p4.html, and 65% of users redirected to p5.html. Users do not need to stick to the page they are first redirected to. They could end up on a different page with every request to p1.html Write a function/pseudocode that would be invoked with every request to p1.html and redirect the correct percentage of users to the correct page. Any suggestions will be of great help.

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• Why hasn't functional programming taken over yet?

  - by pankrax

  I've read some texts about declarative/functional programming (languages), tried out Haskell as well as written one myself. From what I've seen, functional programming has several advantages over the classical imperative style: Stateless programs; No side effects Concurrency; Plays extremely nice with the rising multi-core technology Programs are usually shorter and in some cases easier to read Productivity goes up (example: Erlang) Imperative programming is a very old paradigm (as far as I know) and possibly not suitable for the 21st century Why are companies using or programs written in functional languages still so "rare"? Why, when looking at the advantages of functional programming, are we still using imperative programming languages? Maybe it was too early for it in 1990, but today?

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• Inject a EJB into a JSF converter with JEE6

  - by Michael Bavin

  Hi, I have a stateless EJB that acceses my database. I need this bean in a JSF 2 converter to retreive an entity object from the String value parameter. I'm using JEE6 with Glassfish V3 @EJB annotation does not work and gets a NPE, because it's in the faces context and it has not access to the ejb context. My question is: Is it still possible to Inject this bean (With a @Resource or other annotation, a JNDI lookup,...), or do i need a workaround? Thank you Solution Do a JNDI lookup like this: try { ic = new InitialContext(); myejb= (MyEJB) ic .lookup("java:global/xxxx/MyEJB"); } catch (NamingException e) { e.printStackTrace(); }

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• What is a good practice for handling SQL connections within a WCF call?

  - by Rising Star

  Suppose I want to create a (stateless) WCF service with three methods exposed on an endpoint: performSqlOperationA(), performSqlOperationB(), and performSqlOperationC(). Each method inserts data into a SQL database. The way I've seen things done at my office, each method would begin with code to initialize a SqlConnection object. Each method would end with code to safely dispose it. What is a good practice for coding these WCF methods so that the SqlConnection object is initialized and disposed in each method without having to do these things in each method? I know that I can have the connection initialized in the constructor for the class for the WCF methods, but I don't know about disposing it... The calls cannot be wrapped in a using block. One solution I'm familiar with is PostSharp, which allows me to set an attribute which causes specific code to automatically run at the beginning and end of each method call, but it would be greatly preferable to do this with only the .net framework.

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• apache commons http client efficiency

  - by wo_shi_ni_ba_ba

  I use apache commons http client to send data via post every second, is there a way to make the following code more efficient? I know http is stateless, but is there anything I can do to improve since the base url is always the same in this case(only the parameter value change. private void sendData(String s){ try { HttpClient client = getHttpClient(); HttpPost method = new HttpPost("http://192.168.1.100:8080/myapp"); System.err.println("send to server "+s); List formparams = new ArrayList(); formparams.add(new BasicNameValuePair("packet", s)); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8"); method.setEntity(entity); HttpResponse resp=client.execute(method); String res = EntityUtils.toString(resp.getEntity()); System.out.println(res); } catch (Exception e) { e.printStackTrace(); } } private HttpClient getHttpClient() { if(httpClient==null){ httpClient = new DefaultHttpClient(); } return httpClient; }

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• Is JPA + EJB to much slow (or heavy) for over Internet transactions?

  - by Xavier Callejas

  Hi, I am developing a stand-alone java client application that connects to a Glassfish v3 application for JPA/EJB facade style transactions. In other words, my client application do not connect directly to the database to CRUD, but it transfers JPA objets using EJB stateless sessions. I have scenarios where this client application will be used in an external network connected with a VPN over Internet with a client connection of 512kbp/DSL, and a simple query takes so much time, I'm seeing the traffic graph and when I merge a entity in the client application I see megabytes of traffic (I couldn't believe how a purchase order entity could weight more than 1 mb). I have LAZY fetch in almost every many-to-many relationship, but I have a lot of many-to-one relationships between entities (but this is the great advantage of JPA!). Could I do something to accelerate the the speed of transactions between JPA/EJB server and the remote java client? Thank you in advance.

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• @Intertceptors does not work for web bean for JSF page.

  - by Drevlyanin

  @Named @ConversationScoped @Interceptors(MyInterceptor.class) public class BeanWeb implements Serializable { public String methodThrowException throws Exception() { throws new Exception(); } } public class MyInterceptor { @AroundInvoke public Object intercept(InvocationContext ic) throws Exception { try { return ic.proceed(); } catch (Exception e) { return null; } } } For @Stateless beans interceptor works, but for the BeanWeb interceptor does not work. And we have never entered into "intercept" method. Why is this happening? How could intercept method calls in BeanWeb? P.S.: All this spin under Glassfish 3.x.

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• How to keep statefull web clients in sync, when multiple clients are looking at the same data?

  - by Hilbrand

  In a RIA web client, created with GWT, the state is maintained in the web client, while the server is (almost) stateless (this is the preferred technique to keep the site scalable). However, if multiple users looking at the same data in their browser and one user changes something, which is send to the server and stored in the database, the other users still have the old data in their browser state. For example a tree is shown and one of the users adds/removes an item from the tree. Since there can be a lot of state in the client, what is the best technique to keep the state in the clients in sync? Are there any java frameworks that take care of this?

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• Asp.net session on browser close

  - by budugu

  Note: Cross posted from Vijay Kodali's Blog. Permalink How to capture logoff time when user closes browser? Or How to end user session when browser closed? These are some of the frequently asked questions in asp.net forums. In this post I'll show you how to do this when you're building an ASP.NET web application. Before we start, one fact: There is no full-proof technique to catch the browser close event for 100% of time. The trouble lies in the stateless nature of HTTP. The Web server is out of the picture as soon as it finishes sending the page content to the client. After that, all you can rely on is a client side script. Unfortunately, there is no reliable client side event for browser close. Solution: The first thing you need to do is create the web service. I've added web service and named it AsynchronousSave.asmx.    Make this web service accessible from Script, by setting class qualified with the ScriptServiceAttribute attribute...  Add a method (SaveLogOffTime) marked with [WebMethod] attribute. This method simply accepts UserId as a string variable and writes that value and logoff time to text file. But you can pass as many variables as required. You can then use this information for many purposes. To end user session, you can just call Session.Abandon() in the above web method. To enable web service to be called from page’s client side code, add script manager to page. Here i am adding to SessionTest.aspx page When the user closes the browser, onbeforeunload event fires on the client side. Our final step is adding a java script function to that event, which makes web service calls. The code is simple but effective My Code HTML:( SessionTest.aspx ) C#:( SessionTest.aspx.cs ) That’s’ it. Run the application and after browser close, open the text file to see the log off time. The above code works well in IE 7/8. If you have any questions, leave a comment.

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• Asp.net session on browser close

  - by budugu

  Note: Cross posted from Vijay Kodali's Blog. Permalink How to capture logoff time when user closes browser? Or How to end user session when browser closed? These are some of the frequently asked questions in asp.net forums. In this post I'll show you how to do this when you're building an ASP.NET web application. Before we start, one fact: There is no full-proof technique to catch the browser close event for 100% of time. The trouble lies in the stateless nature of HTTP. The Web server is out of the picture as soon as it finishes sending the page content to the client. After that, all you can rely on is a client side script. Unfortunately, there is no reliable client side event for browser close. Solution: The first thing you need to do is create the web service. I've added web service and named it AsynchronousSave.asmx.    Make this web service accessible from Script, by setting class qualified with the ScriptServiceAttribute attribute...  Add a method (SaveLogOffTime) marked with [WebMethod] attribute. This method simply accepts UserId as a string variable and writes that value and logoff time to text file. But you can pass as many variables as required. You can then use this information for many purposes. To end user session, you can just call Session.Abandon() in the above web method. To enable web service to be called from page’s client side code, add script manager to page. Here i am adding to SessionTest.aspx page When the user closes the browser, onbeforeunload event fires on the client side. Our final step is adding a java script function to that event, which makes web service calls. The code is simple but effective My Code HTML:( SessionTest.aspx ) C#:( SessionTest.aspx.cs ) That’s’ it. Run the application and after browser close, open the text file to see the log off time. The above code works well in IE 7/8. If you have any questions, leave a comment.

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• Creating Asynchronous Methods in EJB 3.1

  - by cindo

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} OBE of the Month: Creating Asynchronous Methods in EJB 3.1 This OBE covers creating an EJB 3.1 application that demonstrates the use of the @Asynchronous annotation in an Enterprise Java Bean (EJB) class or specific method. In this tutorial, you will create a Java EE 6 Web Application and add the following components to it - a Stateless Session Bean with two asynchronous methods. You define a Servlet to call the asynchronous methods and to keep track of the invocation and completion times to demonstrate the asynchronous nature of the method calls. The index.jsp will contain a form with a submit button, Run allowing you to execute the application. The form will submit to the Servlet which invokes the asynchronous methods defined in the session bean and the response is re-directed to response.jsp. Information about the asynchronous handling procedure is displayed to users. From this information, users will notice that the invoker thread and the called asynchronous thread are working concurrently. Check out this new OBE on the Oracle Learning Library: Creating Asynchronous Methods in EJB 3.1. This OBE is part of the new EJB 3.1 New Features Series. Related OBE’s that might interest you: Creating a No-Interface View Session Bean and Packaging in a WAR File Creating and Accessing a Session Bean in a  Web Application

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• Iptables: "-p udp --state ESTABLISHED"

  - by chris_l

  Hi, let's look at these two iptables rules which are often used to allow outgoing DNS: iptables -A OUTPUT -p udp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p udp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT My question is: How exactly should I understand the ESTABLISHED state in UDP? UDP is stateless. Here is my intuition - I'd like to know, if or where this is incorrect: The man page tells me this: state This module, when combined with connection tracking, allows access to the connection tracking state for this packet. --state ... So, iptables basically remembers the port number that was used for the outgoing packet (what else could it remember for a UDP packet?), and then allows the first incoming packet that is sent back within a short timeframe? An attacker would have to guess the port number (would that really be too hard?) About avoiding conflicts: The kernel keeps track of which ports are blocked (either by other services, or by previous outgoing UDP packets), so that these ports will not be used for new outgoing DNS packets within the timeframe? (What would happen, if I accidentally tried to start a service on that port within the timeframe - would that attempt be denied/blocked?) Please find all errors in the above text :-) Thanks, Chris

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• Tracking down the cause of a web service fault running in IIS

  - by BG100

  I have built a web service in Visual Studio 2008, and deployed it on IIS 7 running on Windows Server 2008 R2. It has been extensively tested, handles all errors gracefully and logs any uncaught errors to a file using log4net. The system normally runs perfectly, but occasionally (2 or 3 times a day) a fault occurs and screws up the application which needs an iisreset to get it working again. When the fault occurs I get some random errors that are caught by my catch-all error log, such as: Value cannot be null. Could not convert from type 'System.Boolean' to type 'System.DateTime'. Sequence contains no elements These errors are raised on every request until I manually do an iisreset, but there is no sight of them when the system is running normally. The web service is a stateless request-response application. Nothing is stored in the session. It could be load related, but I doubt it as there are only around 30 or 40 requests per minute. This is proving very tricky to track down. I can't work out what is putting IIS into this bad state, and why it needs an iisreset to get it working again. Nothing is reported in the event log. Can anyone suggest how to enable more extensive logging that might catch this fault? Also, does anyone know what might be causing the problem?

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• Nginx, HAproxy, Unicorn, Rails and Node settings

  - by Julien Genestoux

  Our application is currently only a "regular" web app, with no fancy things like streaming HTTP or websockets. It's mostly a Rails app, served by a few (20 on 2 machines) Unicorn workers, proxied by a venerable nginx server which deals with load balancing. This has been working quite well for the past year and the app now serves between 400 and 800 requests per second at any point during the day. We're soon releasing 2 new APIs, which are both served by a Node application : a websocket one, as well as a long polling HTTP one. (the fancy thing like the Twitter streaming API where HTTP connections never end). They both use the same port on node and since the node app is stateless, we can certainly deploy a few of them to handle the traffic. The app (node) is now deployed in 5 instances and are now listening on 5 different 'private' ports on the same host. We need to put something in front of them to load balance, but also something that is able to deal with sockets (either websocket or HTTP streaming) which are intended to stay 'up' for days. The question is then : what? I read somewhere that HAProxy does a better job than Nginx at this. What do you recommend?

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• should i link to a blog site or install my own blog engine?

  - by dc

  we're setting up a company blog. Our technology stack is .NET. Should we just use blogger/wordpress for the blog and redirect to it from our site? or should i install a blog engine directly on our site (e.g. blogEngine.NET)? some considerations i'd like feedback on are: 1.SEO - if you host your blog on wordpress/blogger instead of installing it on your site - will you get better page rankings? (if the content was the exact same) 2.scalability - i've read that dotNetBlogEngine doesnt scale well on web farms etc. our website is setup to be stateless. 3.security - presumably a hosted blog site has the advantage of having regular security updates. how easy is it to keep an installed blog engine patched? 4.examples of installed blog engines - dotNetBlogEngine seems to be the best but has a couple of limitations. can anyone suggest another one (n/a if you're advice is to host the blog on blogger/wordpress) 5.any other comments/issues/concerns we should be aware of? thanks for your feedback!

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• REMOTE_USER not getting set?

  - by landed

  I am trying to setup LDAP Authentication in Joomla using a plugin called JMapMyLDAP (in fact 4 plugins each doing a different job). I need to pull a part of a string out of the server variable REMOTE_USER and this should be visible (we see here http://timplummer.com.au/4-how-to-integrate-joomla-3-with-active-directory-using-ldap.html) in phpinfo(); The issue is that REMOTE_USER is not set or at least not appearing. A few things to note (if you don't mind) here- conceptually I am not really understanding authentication as a whole subject it appears to be vast despite my years working in websites. Yes I used asp and built php pages to check a user is who they say they are with a token(/session?) that was given to just them and then they are identified when a stateless request is made to the server. Thats my level of understanding. This sounds different to the basic authentication in apache where a password sits in a file and a username and the user needs to login to a basic form to get access to the folder/docs this is via an .htaccess file. Ok so with the LDAP to work I need to get REMOTE_USER this sounds very reasonable as how else do we know is making the request. Thank you.

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• Asp.net Session State Revisited

  - by karan@dotnet

  Every now and then I see doubts and queries which I believe is the most discussed topic in the .net environment - Asp.net Sessions. So what really are they, why are they needed and what does browser and .net do with it. These and some of the other questions I hope to answer with this post. Because of the stateless nature of the HTTP protocol there is always a need of state management in a web application. There are many other ways to store data but I feel Session state is amongst the most powerful one. The ASP.NET session state is a technology that lets you store server-side, user-specific data. Our web applications can then use data to process request from the user for which the session state was instantiated. So when does a session is first created? When we start a asp.net application a non-expiring cookie is created and its called as ASP.NET_SessionId. Basically there are two methods for this depending upon how you configure this setting in your config file. The session ID can be a part of cookie as discussed above(called as ASP.NET_SessionId) or it is embedded in the browser’s URL. For the latter part we have to set cookie-less session in our web.config file. These Session ID’s are 120-bit random number that is represented by 20-character string. The cookie will be alive until you close your browser. If you browse from one app to another within the same domain, then both the apps will use the same session ID to track the session state. Why reuse? so that you don’t have to create a new session ID for each request. One can abandon one particular Session by calling Session.Abandon() which will stop the page processing and clear out the session data. A subsequent page request causes a brand new session object to be instantiated. So what happened to my cookie? Well the session cookie is still there even when one Session.Abandon() is called and another session object is created. The Session.Abandon() lets you clear out your session state without waiting for session timeout. By default, this time-out is a 20-minute sliding expiration. This expiration is refreshed every time that the user makes a request to the Web site and presents the session ID cookie. The Abandon method sets a flag in the session state object that indicates that the session state should be abandoned. If your app does not have global.asax then your session cookie will be killed at the end of each page request. So you need to have a global.asax file and Session_Start() handler to make sure that the session cookie will remain intact once its issued after the first page hit. The runtime invokes global.asax’s Session_OnEnd() when you call Session.Abandon() or the session times out. The session manager stores session data in HttpCache with sliding expiration where this timeout can be configured in the <sessionState> of web.config file. When the timeout is up the HttpCache will remove the session state object. Sometimes we want particular pages not to time out as compared to other pages in our applications. We can handle this in two ways. First, we can set a timer or may be a JavaScript function that refreshes the page after fixed intervals of time. The only thing being the page being cached locally and then the request is not made to the server so to prevent that you can add this to your page: <%@ OutputCache Location="None" VaryByParam="None" %> Second approach is to move your page into its own folder and then add a web.config to that folder to control the timeout. Also not all pages in your application will need access to session state. For those pages that do not, you can indicate that session state is not needed and prevent session data from being fetched from the store in requests to these pages. You can disable the session state at page level like this:<%@ Page EnableSessionState="False" %>tbc…

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