Update web page when database changes

[cguillot]

Hello,

I have a web page that displays information from a SQL database and
this information can change frequently. Basically, a database entry is
made into a table every time a person enters or leaves a defined area
and I need to display this information to a user watching a monitor.
Automatically refreshing the page is not a good option because it would
have to refresh no more than every 5 seconds and the screen flashes are
annoying. I have set up a Cache Dependency for the table and it
creates a file on the server every time there is a change in the table.
I then have a function that compares the last accessed time of the
file so I know when a change has occurred and can then refresh the
page.

How do I get the function to continuously check the file to see if a
change occurred once the page is loaded? Is there a better way to
refresh the data on my page without doing a refresh every few seconds?

Thanks,

Chad

 

[Steve C. Orr [MVP, MCSD]]

Assuming you must have a thin client (no .NET framework on the client) then
the web page must make a request to the server every N seconds to see if
there are any updates. The server cannot contact the client to let it know
about changes.
Since you don't like the screen flashing during the refresh every 5 seconds,
you could use SmartNavigation or some kind of AJAX / XMLHttp / Web Service
solution to have the page make a callback without refreshing the entire
page.

Here's more info:
http://msdn.microsoft.com/library/d...fSystemWebUIPageClassSmartNavigationTopic.asp
http://www.codeguru.com/Csharp/.NET/net_general/tipstricks/article.php/c9679/

This kind of thing gets easier in ASP.NET 2.0 if you can wait until then:
http://www.developer.com/net/asp/article.php/3506896