Caching in ASP.NET with a dependency on the SQL Server
As I suspected when you use caching on ASP.NET 2.0 with SQL Server Dependency in SQL Server 2005 the system is not implemented with a polling mechanis as in previous versions of SQL Server. It uses the NOtifications Services to advise the ASP.NET that some cache item must be cleared. See Caching in ASP.NET with the SqlCacheDependency Class