Implementation question

[Strange Cat]

Hi everyone!

I'm about to start a new project and I'd like to hear from someone more
experienced than me.

What I'm requested to do is:

Display an autorefreshing page that gets data from a SQL Server DB on web
clients: kinda know how to do this, autorefreshing page with HTTP Tag
META... and so on.

What I'm begin asked to do is NOT TO QUERY THE DB every time the page
refreshes, but instead keep the data in memory (an Application.Item would be
ok I guess) and refresh the data in Application.Item ONLY when a change
occurs in DB Data.

I would also write a separate (Windows Forms) program that gathers data and
updates the DB.

What's the problem, then? How can I INFORM the ASPNET application that data
has changed in DB and it's time to refresh the data in Application memory?
Use a Webservice? Really dunno...

Thanx in advance for any idea.

ASC

 

[msnews.microsoft.com]

If you told us what you were doing it would be a big help. Storing data in
application memory? Why not just have the database or a windows service
update an XML file and display it to page? You can set refresh to 5 seconds
then without worrying about hitting the server.

Otherwise there are lots of ways to cache data so it's not pulling from the
database everytime. Your slowest point of your application is going to be
every time you make a new page request or refresh the page. I hate to use
autorefresh. Your connection goes bad and your user is looking at a blank
page.

You can never push data using HTTP. HTTP is a request-response synchronous
action. There is a way to push data to the web browser, by using Flash,
Java, and sockets, but sockets create a huge load to the server.

-Max

Hi everyone!

I'm about to start a new project and I'd like to hear from someone more
experienced than me.

What I'm requested to do is:

Display an autorefreshing page that gets data from a SQL Server DB on web
clients: kinda know how to do this, autorefreshing page with HTTP Tag
META... and so on.

BAD IDEA.

What I'm begin asked to do is NOT TO QUERY THE DB every time the page
refreshes, but instead keep the data in memory (an Application.Item would be
ok I guess) and refresh the data in Application.Item ONLY when a change
occurs in DB Data.

Then why refresh the page? Try using Flash or Java to push data to the
client.

I would also write a separate (Windows Forms) program that gathers data and
updates the DB.

Sounds like a job for a Windows Service. Use Windows app to set a config
file. Load the service on your web server to run at start up and read the
config file.

What's the problem, then? How can I INFORM the ASPNET application that data
has changed in DB and it's time to refresh the data in Application memory?
Use a Webservice? Really dunno...

Web services are used for interoperability

 

[Strange Cat]

[CUT]

Thanx for answering Max.

The project I'm about to start monitors data coming from a proprietary
network of badge readers (the ones used to open doors).

So there is a windows forms program that is "connected" to the network via a
non managed DLL which gathers data from the proprietary network (badges ids
being read) and stores them in a SQL Server DB.

Some Web clients (with autorefresh) display data from the DB.

As I stated before, I don't know how to inform the ASPNET app when to read
new data from the DB, and honestly I didn't understand your answer about
displaying XML on the browsers. The graphics design matters, and I don't
think XML would look very nice on a browser windows.

It's no easy task for my limited ASPNET experience...

Thanx

ASC

 

[Strange Cat]

[CUT]

Sorry, forgot: I know like nothing about Flash and Java...

Bye

ASC

 

[Hans Kesting]

Hi everyone!

I'm about to start a new project and I'd like to hear from someone more
experienced than me.

What I'm requested to do is:

Display an autorefreshing page that gets data from a SQL Server DB on web
clients: kinda know how to do this, autorefreshing page with HTTP Tag
META... and so on.

What I'm begin asked to do is NOT TO QUERY THE DB every time the page
refreshes, but instead keep the data in memory (an Application.Item would be
ok I guess) and refresh the data in Application.Item ONLY when a change
occurs in DB Data.

I would also write a separate (Windows Forms) program that gathers data and
updates the DB.

What's the problem, then? How can I INFORM the ASPNET application that data
has changed in DB and it's time to refresh the data in Application memory?
Use a Webservice? Really dunno...

Thanx in advance for any idea.

ASC

A google search for "database cache dependency asp.net" lead to this link:
www.eggheadcafe.com/articles/20030716.asp

The data (read from the database) is stored in the Cache, with a dependency
on the database (through some tricks), so the cached data is removed when
the database has changed.
Have not tried it, but sounds promising.

Hans Kesting

 

[Strange Cat]

[CUT]

Thanx for answering Hans, you did what I should have done, google... but I
didn't know how to put down a google query for asking that... My english
isn't good enough.

Thanx a lot! I will surely read and test what is explained there!

Bye

ASC

 

[Hans Kesting]

[CUT]

Thanx for answering Hans, you did what I should have done, google... but I
didn't know how to put down a google query for asking that... My english
isn't good enough.

Thanx a lot! I will surely read and test what is explained there!

Bye

ASC

Thought so. IF you known the right keywords, it's not difficult. The trick
is finding those keywords (that's why I mentioned them) ...

Hans Kesting

 

[Joe Fallon]

Keep reading.
He wrote a follow up article that uses the same technique as ASP.Net 2.0.
I implemented it and it works well.
But read my comments at the bottom of the page as the article does not fully
cover everything.
--
Joe Fallon

[CUT]

Thanx for answering Hans, you did what I should have done, google... but I
didn't know how to put down a google query for asking that... My english
isn't good enough.

Thanx a lot! I will surely read and test what is explained there!

Bye

ASC

Thought so. IF you known the right keywords, it's not difficult. The trick
is finding those keywords (that's why I mentioned them) ...

Hans Kesting

 

[msnews.microsoft.com]

It sounds like with your skill, you are doing it the best way you can. This
seems like a specialized web app that won't have 100's of people accessing
it at the same time, so you don't really need to worry about caching until
you start seeing it slow down. Set the browser to refresh a set interval.
Just query the database each time. Then tell your boss not to forget to
test it, so he doesn't blame you if 1000 people get on at once and crash it.

-Max