How can I signal a c# console app from SQL Server?

Rather than poll against some tables, I'd like to signal a waiting c# app that there are new rows to be processed in a table, maybe via a trigger. Is there some way for the database to signal to a cons开发者_运维百科ole app, or am I stuck polling the table looking for new rows?

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Take a look at Query Notifications (SQL Server 2005+).

Microsoft SQL Server 2005 introduces query notifications, new functionality that allows an application to request a notification from SQL Server when the results of a query change. Query notifications allow programmers to design applications that query the database only when there is a change to information that the application has previously retrieved.

There is an example here of how to write a simple form app to register a query for notification: http://msdn.microsoft.com/en-us/library/a52dhwx7(VS.80).aspx.

This does require the Service Broker to be enabled on the database.

You should take a look at the notes in the Remarks section of the MSDN SqlDependency documentation to make sure it is the right choice for your scenario

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Check if SqlCacheDependency can be of any use...

http://www.asp.net/data-access/tutorials/using-sql-cache-dependencies-cs

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If it is SQL Server 2008, You can use Event-Based Activation using Service Broker as well.

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I have used WCF with SQLCLR to get data from another process into SQL, worked pretty good apart from some minor quirks to set it up. So you can just call other processes from SQl this way. It's usually quite hard to deploy to customers though, DBA don't like this sort of stuff.

GJ

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Check out SQL Service Broker. Using a Queue and the WAITFOR syntax I have changed a custom polling service into a blocking/signal service. You could also look at the event-activation. Either way this would allow for a transactional way to call your external program in a non-polling async way that will not slow down triggers and database locks.