Query Notification in SQL 2005

Query Notification in SQL 2005 can be used to send a query to SQL Server and request that a notification be generated if executing the same query produces different results from those obtained initially. That means if any row in one of the tables included in the query is changed, .NET code will get an automatic notification.
MSDN Link: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvs05/html/querynotification.asp