----------------------------------------------------------- New Message on BDOTNET
----------------------------------------------------------- From: SitaramanM Message 4 in Discussion Hi As pooran suggested web services can be used. But web services by itself is not enough for your requirement and neither is it the only option. there is much more to it here than what meets the eye. Your requirement is that there will be certain events that will be happening at the server level and whenever these events(lets say data change like stock prices falling) then the client application needs to be notified bout the same. Right!!!!! One option is polling the server database. This is a old and dumb technique and not for professional applications. Two features of .Net that allow you to the achieve the functionality that u desire are : a) Events, Delegates and Callbacks b) Remoting You need to use a mix of these two features to create the ap tht u want. MSDN offers extensive material for these topics. In fact there is a example in MSDN which combines the Remoting and Events,Delegates and CallBacks to create a simple chat application(The original example had a bug and MS has posted the updated code at http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/q312/1/14.asp&NoWebContent=1). The following is the programming approach tht i would suggest Server-Application a) Your business application will be running on the server(in ur case i guess the asp application) b) Create a Remoting Server application(preferrably Singleton) c) Define public Events in the Remoting Server Aplications d) Expose events from the Remoting Server Application e) Declare some public functions in Remoting Server Application. which will raise the event f) When the data is changed thru the business application, perform the data changes(more on this later in the Note below) g) After the data is Changed Notify the Remoting Server Application thru normal function calls exposed by the Remoting Server App h) From the Called Remoting Server App Functions, Raise the events from Remoting Server Application passing the Changed Data as parameter(wish i could raise events of the Remoting Server App from th business function itself. but i dont think it is possible. In fact if i am right u cannot even raise an event of a parent class from the c hild class. if it is not possible from a child class then i dont think it will be possible from a object instance) i) Return to the calling function Client-Application a) Create a VB Appplication that runs on th systray b) Make this a Remoting Client Application c) Create the Remoting configuration file(can do it thru code also, but suggest config file here) to connect to the Remoting Server App defined in step b) of the Server -Application that you have created d) Subscribe to the events by writing Event Handler Function e) In the Event Handler functions write code to display the data Note : In this case you need to call into the Remoting Server application every time a data is changed. You can centralise this functionality somewhere else for ease of development. If the changes are database specific, then instead of calling the RemotingServer APP functions in every business function after data change , you can probably use triggers in the tables which call extended stored procedures, which i believe can be written in .Net. This is a gray area for me, as DB has never been my forte, but you can check out Gaurav's source code example in http://www.wintoolzone.com/processor.aspx?ID=90 which talks about "how to use managed code from SQL Server 2000 extended stored procedures." and i believe this should help u out. This is also one of the options available to you. However as a rough start you can skip this and call the Remoting Server App functions from the business functions directly and later enhance it So look up the msdn for the article and sample i mentioned above and then prototype a sample based on the steps mentioned above. In case of any issues do post ur queries. I had fooled around with such an application(A bank application which sends notifications to customers when there is a transaction in their account) but dont seem to have it with me here. Will try to post the sample if i get hold of it... hth regards, sr ----------------------------------------------------------- To stop getting this e-mail, or change how often it arrives, go to your E-mail Settings. http://groups.msn.com/BDotNet/_emailsettings.msnw Need help? If you've forgotten your password, please go to Passport Member Services. http://groups.msn.com/_passportredir.msnw?ppmprop=help For other questions or feedback, go to our Contact Us page. http://groups.msn.com/contact If you do not want to receive future e-mail from this MSN group, or if you received this message by mistake, please click the "Remove" link below. On the pre-addressed e-mail message that opens, simply click "Send". Your e-mail address will be deleted from this group's mailing list. mailto:[EMAIL PROTECTED]
