If I leave my current page on a asp.net Web application I want that all sessions get destroyed. For that I am using Session.Abandon() on Page_Unload Event. But if I do a Postback with a normal Button_Click I don't want to fire this event.
It would be awesome if you could help me.
Lingo
First you need to understand how the web works. When you access stackoverflow.com for example your are actualy seeing the past. The page you accessed it's already destroyed on the web server.
Based on that principle when you use Page_Unload or Session.Abandon if you actually close your browser you don't send any request for the web server so the web server didn't know (and don't care even) if you close your page.
For doing like
The page unload description act like this it's after being rendered it's had nothing with the close of the page.
"The Unload event is raised after the page has been fully rendered, sent to the client, and is ready to be discarded.
At this point, page properties such as Response and Request are unloaded and cleanup is performed.'
Reference (https://msdn.microsoft.com/en-us/library/ms178472.aspx)
You need to use javascript for doing this behaviour or try the new websocket that will keep the connection alive and the server could check if the client has lost the link with the server.
I want to silently check for Session existence without Posting back page by using AJAX Timer and AsyncPostBack Trigger.
Now, I would like to know is there anyway to silently check whether ASP.NET C# if (Session["email"] = null) { Response.Redirect("Logout.aspx"); } something of this kind to check for every 10 seconds without Posting Back Page and without using AJAX by using something like jQuery or any other technology that is supported by .NET?
The server can push to a loaded page if you use an asynchronous controller with a partial view which is loading every set amount of time.
http://msdn.microsoft.com/en-us/library/ee728598.aspx
there is only one way to get to the server. send a request. that can be a "standard" request where the browser will refresh the screen when a response is sent. the other type of request is a ajax request. the difference is an ajax request contains a header to inform the server it's an ajax request. when the browser receives the response it will allow the developer to decide what to do with the response. either way a full request/response exchange takes place the only difference is how the browser handles the request.
jquery is a javascript library that includes functionality to make ajax request easier to setup.
to answer you question no, there is no way around making a request.
I'm calling a static Page method via javascript that takes between 5s and 10 min. I'd like to give my user the choice to either continue waiting for the request to complete or not, and use window.setTimeout() to check back every 30s.
I've tried both location.href = '/newpage.aspx' or firing a button's click handler (which does similar redirect) to redirect the user prior to completion of the page method, to no avail. I can immediately send user to a simple html page, but a redirect to any aspx page involving server-side appears to block. When the page method finally completes, the redirect does succeed.
Is this:
a browser issue? If all modern
browsers support at least 2
concurrent requests per domain, why
wouldn't this work?
a framework
limitation?
a desirable design
pattern or even possible? I've
checked, and after redirecting to an
HTML page, the original request continues processing (db updates, no problem).
Are Page method calls simply not asynchronous from a "concurrent HTTP request" perspective?
Any insight greatly appreciated!
It sounds like you're blocking on InProc Session, which is limited to one concurrent request per unique session. If you don't need access to the Session in your page method, you can disable it by modifying the WebMethod attribute:
[System.Web.Services.WebMethod(EnableSession=false)]
I have a long-running database query that I've placed in an asynchronous AJAX callback (or so I think) to allow the user to navigate to another page if they're not interested in the results.
Whether I call the query automatically after page load or on click, the page always locks up until it returns, i.e links and buttons don't work. Internet Explorer 6's own menus are fine however, so it's not that IE itself is overworked.
What could I be doing wrong? It seems as though my request isn't really asynchronous. Here is a code snippet:
this.XmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
this.XmlHttp.open("POST", url, true);
this.XmlHttp.send(data);
It's not the browser that blocks the page, it's the server.
IIS only handles one request at a time from each user. As the user already has a request from the AJAX call that the server is working on, the new request will be queued until the first request is handled.
To keep the long running request from blocking the user on the server you have to make the page that the AJAX call gets session-less. That way it's not associated to the user.
What is difference between Server.Transfer and Response.Redirect?
What are advantages and disadvantages of each?
When is one appropriate over the other?
When is one not appropriate?
Response.Redirect simply sends a message (HTTP 302) down to the browser.
Server.Transfer happens without the browser knowing anything, the browser request a page, but the server returns the content of another.
Response.Redirect() will send you to a new page, update the address bar and add it to the Browser History. On your browser you can click back.
Server.Transfer() does not change the address bar. You cannot hit back.
I use Server.Transfer() when I don't want the user to see where I am going. Sometimes on a "loading" type page.
Otherwise I'll always use Response.Redirect().
To be Short: Response.Redirect simply tells the browser to visit another page. Server.Transfer helps reduce server requests, keeps the URL the same and, with a little bug-bashing, allows you to transfer the query string and form variables.
Something I found and agree with (source):
Server.Transfer is similar in that it sends the user to another page
with a statement such as Server.Transfer("WebForm2.aspx"). However,
the statement has a number of distinct advantages and disadvantages.
Firstly, transferring to another page using Server.Transfer
conserves server resources. Instead of telling the browser to
redirect, it simply changes the "focus" on the Web server and
transfers the request. This means you don't get quite as many HTTP
requests coming through, which therefore eases the pressure on your
Web server and makes your applications run faster.
But watch out: because the "transfer" process can work on only those
sites running on the server; you can't use Server.Transfer to send
the user to an external site. Only Response.Redirect can do that.
Secondly, Server.Transfer maintains the original URL in the browser.
This can really help streamline data entry techniques, although it may
make for confusion when debugging.
That's not all: The Server.Transfer method also has a second
parameter—"preserveForm". If you set this to True, using a statement
such as Server.Transfer("WebForm2.aspx", True), the existing query
string and any form variables will still be available to the page you
are transferring to.
For example, if your WebForm1.aspx has a TextBox control called
TextBox1 and you transferred to WebForm2.aspx with the preserveForm
parameter set to True, you'd be able to retrieve the value of the
original page TextBox control by referencing
Request.Form("TextBox1").
Response.Redirect() should be used when:
we want to redirect the request to some plain HTML pages on our server or to some other web server
we don't care about causing additional roundtrips to the server on each request
we do not need to preserve Query String and Form Variables from the original request
we want our users to be able to see the new redirected URL where he is redirected in his browser (and be able to bookmark it if its necessary)
Server.Transfer() should be used when:
we want to transfer current page request to another .aspx page on the same server
we want to preserve server resources and avoid the unnecessary roundtrips to the server
we want to preserve Query String and Form Variables (optionally)
we don't need to show the real URL where we redirected the request in the users Web Browser
Response.Redirect redirects page to another page after first page arrives to client. So client knows the redirection.
Server.Transfer quits current execution of the page. Client does not know the redirection. It allows you to transfer the query string and form variables.
So it depends to your needs to choose which is better.
"response.redirect" and "server.transfer" helps to transfer user from one page to other page while the page is executing. But the way they do this transfer / redirect is very different.
In case you are visual guy and would like see demonstration rather than theory I would suggest to see the below facebook video which explains the difference in a more demonstrative way.
https://www.facebook.com/photo.php?v=762186150488997
The main difference between them is who does the transfer. In "response.redirect" the transfer is done by the browser while in "server.transfer" it’s done by the server. Let us try to understand this statement in a more detail manner.
In "Server.Transfer" following is the sequence of how transfer happens:-
1.User sends a request to an ASP.NET page. In the below figure the request is sent to "WebForm1" and we would like to navigate to "Webform2".
2.Server starts executing "Webform1" and the life cycle of the page starts. But before the complete life cycle of the page is completed “Server.transfer” happens to "WebForm2".
3."Webform2" page object is created, full page life cycle is executed and output HTML response is then sent to the browser.
While in "Response.Redirect" following is the sequence of events for navigation:-
1.Client (browser) sends a request to a page. In the below figure the request is sent to "WebForm1" and we would like to navigate to "Webform2".
2.Life cycle of "Webform1" starts executing. But in between of the life cycle "Response.Redirect" happens.
3.Now rather than server doing a redirect , he sends a HTTP 302 command to the browser. This command tells the browser that he has to initiate a GET request to "Webform2.aspx" page.
4.Browser interprets the 302 command and sends a GET request for "Webform2.aspx".
In other words "Server.Transfer" is executed by the server while "Response.Redirect" is executed by thr browser. "Response.Redirect" needs to two requests to do a redirect of the page.
So when to use "Server.Transfer" and when to use "Response.Redirect" ?
Use "Server.Transfer" when you want to navigate pages which reside on the same server, use "Response.Redirect" when you want to navigate between pages which resides on different server and domain.
Below is a summary table of which chalks out differences and in which scenario to use.
The beauty of Server.Transfer is what you can do with it:
TextBox myTxt = (TextBox)this.Page.PreviousPage.FindControl("TextBoxID");
You can get anything from your previous page using the above method as long as you use Server.Transfer but not Response.Redirect
In addition to ScarletGarden's comment, you also need to consider the impact of search engines and your redirect. Has this page moved permanently? Temporarily? It makes a difference.
see: Response.Redirect vs. "301 Moved Permanently":
We've all used Response.Redirect at
one time or another. It's the quick
and easy way to get visitors pointed
in the right direction if they somehow
end up in the wrong place. But did you
know that Response.Redirect sends an
HTTP response status code of "302
Found" when you might really want to
send "301 Moved Permanently"?
The distinction seems small, but in
certain cases it can actually make a
big difference. For example, if you
use a "301 Moved Permanently" response
code, most search engines will remove
the outdated link from their index and
replace it with the new one. If you
use "302 Found", they'll continue
returning to the old page...
There are many differences as specified above. Apart from above all, there is one more difference. Response.Redirect() can be used to redirect user to any page which is not part of the application but Server.Transfer() can only be used to redirect user within the application.
//This will work.
Response.Redirect("http://www.google.com");
//This will not work.
Server.Transfer("http://www.google.com");
Transfer is entirely server-side. Client address bar stays constant. Some complexity about the transfer of context between requests. Flushing and restarting page handlers can be expensive so do your transfer early in the pipeline e.g. in an HttpModule during BeginRequest. Read the MSDN docs carefully, and test and understand the new values of HttpContext.Request - especially in Postback scenarios. We usually use Server.Transfer for error scenarios.
Redirect terminates the request with a 302 status and client-side roundtrip response with and internally eats an exception (minor server perf hit - depends how many you do a day) Client then navigates to new address. Browser address bar & history updates etc. Client pays the cost of an extra roundtrip - cost varies depending on latency. In our business we redirect a lot we wrote our own module to avoid the exception cost.
Response.Redirect is more costly since it adds an extra trip to the server to figure out where to go.
Server.Transfer is more efficient however it can be a little mis-leading to the user since the Url doesn't physically change.
In my experience, the difference in performance has not been significant enough to use the latter approach
Server.Transfer doesn't change the URL in the client browser, so effectively the browser does not know you changed to another server-side handler. Response.Redirect tells the browser to move to a different page, so the url in the titlebar changes.
Server.Transfer is slightly faster since it avoids one roundtrip to the server, but the non-change of url may be either good or bad for you, depending on what you're trying to do.
Response.Redirect: tells the browser that the requested page can be found at a new location. The browser then initiates another request to the new page loading its contents in the browser. This results in two requests by the browser.
Server.Transfer: It transfers execution from the first page to the second page on the server. As far as the browser client is concerned, it made one request and the initial page is the one responding with content.
The benefit of this approach is one less round trip to the server from the client browser. Also, any posted form variables and query string parameters are available to the second page as well.
Just more details about Transfer(), it's actually is Server.Execute() + Response.End(), its source code is below (from Mono/.net 4.0):
public void Transfer (string path, bool preserveForm)
{
this.Execute (path, null, preserveForm, true);
this.context.Response.End ();
}
and for Execute(), what it is to run is the handler of the given path, see
ASP.NET does not verify that the current user is authorized to view the resource delivered by the Execute method. Although the ASP.NET authorization and authentication logic runs before the original resource handler is called, ASP.NET directly calls the handler indicated by the Execute method and does not rerun authentication and authorization logic for the new resource. If your application's security policy requires clients to have appropriate authorization to access the resource, the application should force reauthorization or provide a custom access-control mechanism.
You can force reauthorization by using the Redirect method instead of the Execute method. Redirect performs a client-side redirect in which the browser requests the new resource. Because this redirect is a new request entering the system, it is subjected to all the authentication and authorization logic of both Internet Information Services (IIS) and ASP.NET security policy.
-from MSDN
Response.Redirect involves an extra round trip and updates the address bar.
Server.Transfer does not cause the address bar to change, the server responds to the request with content from another page
e.g.
Response.Redirect:-
On the client the browser requests a page http://InitiallyRequestedPage.aspx
On the server responds to the request with 302 passing the redirect address http://AnotherPage.aspx.
On the client the browser makes a second request to the address http://AnotherPage.aspx.
On the server responds with content from http://AnotherPage.aspx
Server.Transfer:-
On the client browser requests a page http://InitiallyRequestedPage.aspx
On the server Server.Transfer to http://AnotherPage.aspx
On the server the response is made to the request for http://InitiallyRequestedPage.aspx passing back content from http://AnotherPage.aspx
Response.Redirect
Pros:-
RESTful - It changes the address bar, the address can be used to record changes of state inbetween requests.
Cons:-
Slow - There is an extra round-trip between the client and server. This can be expensive when there is substantial latency between the client and the server.
Server.Transfer
Pros:-
Quick.
Cons:-
State lost - If you're using Server.Transfer to change the state of the application in response to post backs, if the page is then reloaded that state will be lost, as the address bar will be the same as it was on the first request.
Response.Redirect
Response.Redirect() will send you to a new page, update the address bar and add it to the Browser History. On your browser you can click back.
It redirects the request to some plain HTML pages on our server or to some other web server.
It causes additional roundtrips to the server on each request.
It doesn’t preserve Query String and Form Variables from the original request.
It enables to see the new redirected URL where it is redirected in the browser (and be able to bookmark it if it’s necessary).
Response. Redirect simply sends a message down to the (HTTP 302) browser.
Server.Transfer
Server.Transfer() does not change the address bar, we cannot hit back.One should use Server.Transfer() when he/she doesn’t want the user to see where he is going. Sometime on a "loading" type page.
It transfers current page request to another .aspx page on the same server.
It preserves server resources and avoids the unnecessary roundtrips to the server.
It preserves Query String and Form Variables (optionally).
It doesn’t show the real URL where it redirects the request in the users Web Browser.
Server.Transfer happens without the browser knowing anything, the browser request a page, but the server returns the content of another.