Datagrid不会刷新已更改的数据

Question

Is there any way to have a datagrid listen to the database and automatically update the data if the database data is changed? I use a SQL Server database.

I'd like to use Linq-2-SQL if possible

Answer 1

Because @Slaggg asked: there are fairly straightforward ways of doing this, but they're almost certainly going to involve a lot of coding, it'll impact performance pretty significantly, and my strong suspicion is that it'll be more trouble than it's worth.

That said, for a typical n-tier application, at a very high level you'll need:

(1) A way to notify the middle tier when the data changes. You could use custom-code triggers inside each the table that fire off some sort of notification (perhaps using WCF and CLR stored procedures), or you could use a SqlDependency object. Probably the second would work better.

(2) A way to notify each client connected to that middle tier. Assuming that you're using WCF, you'll need to use one of the duplex bindings that are available, such as Net.TCP or HttpPollingDuplex (for Silverlight). You'll need to make sure this is configured correctly on both the client and the server. You'll also need to manually keep track of which clients might be interested in the update, so that you can know which ones to update, and you'll need to be able to remove them from that list when they go away or timeout. Tomek, from the MS WCF team, has some pretty good examples on his blog that you might want to investigate.

(3) A mechanism to update the local client's model and/or viewmodel and/or UI once you get the notification from the middle tier that something has changed. This is more complicated than you'd think: it's difficult enough to keep your UI in sync with your data model under normal circumstances, but it gets dramatically more complicated when that data model can be changing under you from the other direction as well.

The idea behind these sorts of notifications is straightforward enough: but getting all the details right is likely to keep you debugging way into the night. And the guy who has to support all this two years from now will curse your name.

Hope this helps.

Answer 2

It depends from where you are updating the database:

• From the same context (in Silverlight, are you adding, deleting, editing on the same page)
• From a ChildWindow in your Silverlight application
• From an external, non-related tool, outside of your Silverlight application