notification of changes between apps on different pc's on the network

[Jurjen de Groot]

I will be developping a planning application for wich it's necessary for
multiple users to view and edit the same data, all changes made by one user,
must be visible to the other user's more or less immediately (on their pc).
So I'm looking for a mechanism with wich I can notify the 'other'
applications on the network of any changes so they can update their 'view'
if necessary.

Although I think I'm capable of solving this problem by re-inventing the
wheel, I'm pretty sure it's already been done, and probably better and more
robust than my first few attempts would be... So can anyone help me out ?


thanks,
Jurjen.

[Michel Posseth [MCP]]

Well i can think of 3 easy ways of acomplishing that


1. if you use SQL server as database backend you could setup notification
services the database performs a callback to your app whenever the dataset
you subscibed to has a change

2. You could create a change mechanism yourself ,,, actually i have done
this a few years ago before we had notification services the following way
let a trigger in your database create a new guid in a watch table
whenever there are changes made in the main table ( you could even implement
this with a low entry "database" as ACCESS however then you should do this
from code .

now when you app gets its dataset it will also retrieve the guid and compare
this once in a while with a backgound thread to the current database value
if it has changed if it has changed you know there are changes and thus need
to update your working set .

3. You could do a broadcast on the network whenever one of the applications
perfomed a change on the dataset , then all running instances can update
there datasets

Maybe someone else has some more ideas !?

regards
Michel Posseth [MCP]
http://www.vbdotnetcoder.com

Post by Jurjen de Groot
I will be developping a planning application for wich it's necessary for
multiple users to view and edit the same data, all changes made by one
user, must be visible to the other user's more or less immediately (on
their pc). So I'm looking for a mechanism with wich I can notify the
'other' applications on the network of any changes so they can update their
'view' if necessary.
Although I think I'm capable of solving this problem by re-inventing the
wheel, I'm pretty sure it's already been done, and probably better and
more robust than my first few attempts would be... So can anyone help me
out ?
thanks,
Jurjen.

[Jurjen de Groot]

Michel,

thanks for your reply, in the mean Time I have found several articles
concerning PublishSubscribe scenario's and am looking into a solution
created by juval lowy from idesign wich seem to do the trick,

thanks.

Post by Michel Posseth [MCP]
Well i can think of 3 easy ways of acomplishing that
1. if you use SQL server as database backend you could setup notification
services the database performs a callback to your app whenever the dataset
you subscibed to has a change
2. You could create a change mechanism yourself ,,, actually i have done
this a few years ago before we had notification services the following way
let a trigger in your database create a new guid in a watch table
whenever there are changes made in the main table ( you could even
implement this with a low entry "database" as ACCESS however then you
should do this from code .
now when you app gets its dataset it will also retrieve the guid and
compare this once in a while with a backgound thread to the current
database value if it has changed if it has changed you know there are
changes and thus need to update your working set .
3. You could do a broadcast on the network whenever one of the
applications perfomed a change on the dataset , then all running instances
can update there datasets
Maybe someone else has some more ideas !?
regards
Michel Posseth [MCP]
http://www.vbdotnetcoder.com

Post by Jurjen de Groot
I will be developping a planning application for wich it's necessary for
multiple users to view and edit the same data, all changes made by one
user, must be visible to the other user's more or less immediately (on
their pc). So I'm looking for a mechanism with wich I can notify the
'other' applications on the network of any changes so they can update
their 'view' if necessary.
Although I think I'm capable of solving this problem by re-inventing the
wheel, I'm pretty sure it's already been done, and probably better and
more robust than my first few attempts would be... So can anyone help me
out ?
thanks,
Jurjen.