Silverlight synchronization

Question

Hello,

Im developing a silverlight app and I need to synchronize a list in different silverlight instances that can be offline. I'll have a server online to sync them.

So we can imagine this:

pc1: A1 A2 A3

pc2: A1 A2 (A3 deleted)

server: A1 A2 A3 (deletes A3 to reflect pc2 and then updates pc1 to also delete)

It must reflect reorder of the items too. I'll want to use this with silverlight online and offline (out of the browser).

Has any of you solved a problem similar to this one? What are good approaches to it?

Thank you, Artur

Answer 1

In a normal disconnected environment you'd use something like Synchronization Services to handle this, but that's a little heavy-weight to have on the Silverlight client.

I'd start by giving each item in the list a GUID. Then I'd maintain a log of inserts, updates, and deletes of the list on each client and on the server. Then every time a client connects to the server you have to do a merge synchronization. In that case you have to detect and handle conflicts:

• Someone edits an item, while someone else deletes it
• Two clients edit an item simultaneously

Your requirement to handle re-ordering of items adds some complexity. You might want to log a re-ordering as a "moved before item x" or "moved after item x" action, rather than updating all the indexes of all items in the list.