I need to be able to refresh a ASPX page if the current data being displayed has changed. How could this be done?
- Marc
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Its not possible automatically. You need to do this in a event.
For example you can write code to refresh your page every 1 minute (or whatever time you prefer). If the Data display code is in the Page Load event then the current data will be retrieved and shown automatically. Its time consuming and irritates the user also.
So, you can specify a button "Refresh Data" and write the code on the click event of the button to show the current data!
Basically you can't do that.
Http uses a disconnected paradigm, which means the server cannot send anything to the client unless the client requests it. So in practice, when something changes on your server (client A makes a change to the data and sends this to the server for update) there is *no* way in Http for the server to send this to client B who is browsing the page.
2 solutions are possible :
1/ Like everyone proposed, do an automatic refresh of the page every X seconds. Now, if you can input data in this page, this is a very very bad idea of course ;)
Or alternativately, if you can, put the non-editable part of the data in an Iframe or a frame and refresh only the frame.
Or finally, provide a refresh button that the user would use to update data (I repeat, the user HAS to request data for it to be sent to him, the server cannot do this automatically).
The choice between an automatic refresh and a user refresh depends on the type of application you have, you should be able to choose which one is best for you.
2/ Second possibility uses embedded controls, or java applets (or even embedded flash ... don't know too much about this). You'd basically establish a TCP as a client/server from the applet/control to a TCP client/server which would be setup on the same machine as your IIS server (for simplicity).
On load, send a "UserReadingPage" event, on unload send a "UserLeftPage" to the IIS machine server.
On a data change, the Web app would send a refresh command to the TCP app located on the IIS machine, which would in turn multicast the refresh command to every client.
Now, you have lots of problem with this solution :
- it's heavy
- it's a damn lot of programming if you've never done this (speaking from experience ^^;)
- you'll run into security problems (for instance, the average user on the internet would have the settings necessary to run this kind of control if it were an embedded control)
- finally, you'll wonder if it was necessary to do all that when a hand refresh can do all this more robustly ;)
If you choose this path though, you might want to embed the data itself in the control, that would be easier to develoo.
All in one, I'll say it again, it depends on your solution, but I'd strongly advise going with the automatic or hand refresh approach. If you *really* need real-time data refresh, you'd be much better leaving Web app and coding a Tcp app instead (not a feasible solution sometimes unfortunately ...).
Basically what you want to do in that case is have one app on the IIS machine and have the other apps on the client.
Both would have to listen for connections, and while being continuously receiving also be able to send to the other machine.
You want an asynchronous server in your case (at least for the IIS machine app) due to the number of possible clients, which is going to be a bit harder to code but doesn't block.
Simplest thing to use are TCPClient/TCPListener, you might want to check the MSDN help for them, as well as :
http://www.codeproject.com
http://www.csharphelp.com/
If that doesn't help, I'll give a look at work to see if I can get a sample code.
hello all,
I have Visual Studio .NET 2000 as well as 2003 installed on my machine. I have Windows 2000 professional for OS. I get the error "Unable to debug on the web server" when I try to debug a project in 2003. However, I can debug on 2000 version. I have set debug=true in machine.config for framework 1.1 and re-started IIS services many times over.
Can anybody help me get my debugger running on 2003.
Thanks
Supriya
Hi Supriya,
may be this will help for the debugging problem,
http://msdn.microsoft.com/
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by: dxz2Posted on 2004-01-21 at 03:46:43ID: 10163835
Hi,
the problem is that when your browser opens the page,it opens it from the cache and not from the sourse..
so in order to make the browser no to do that everytime you opens
the page you have to write in the header of every page the following:
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">
but the best way to make this if you are using more that one page to view the data is
to make one asp file that contains a code inside it,and just include it to every page
by writing the include statment at the top of every page.
Example.
this is the ASP file that you need ,you have to save it as no_cache.asp,
<%
Response.Expires = 60
Response.Expiresabsolute = Now() - 1
Response.AddHeader "pragma","no-cache"
Response.AddHeader "cache-control","private"
Response.CacheControl = "no-cache"
Response.CacheControl = "no-cache"
Response.AddHeader "Pragma", "no-cache"
Response.Expires = -1
Response.Write "<script language='JavaScript'>"
Response.Write "window.status=' '"
Response.Write "</script>"
%>
then include it like the following on the page top,where you want to view the data:
<!-- #include file="no_cahce.asp" -->