sql server 2008 - sqlcachedependency without trigger?

I am so puzzled.

I am using this open-source snippet. I have a table without any triggers in SQL Server, and yet the SQLCacheDependency is working fine. I thought you needed triggers on the table for it to work?!

                DateTime localFileTimeStamp = DateTime.Now; 
                DateTime fileTimeStampInDB;
                string cacheKey = string.Format("ImageId_{0}", 1);
                object o = Utils.Cache.Get(cacheKey);
                if (null == o)
                {
                    // get timestamp from DB
                    SqlCacheDependency dep;
                    fileTimeStampInDB = DataLayer.GetTimeStamp(1, out dep);
                    Utils.Cache.Insert(cacheKey, fileTimeStampInDB, dep, Cache.NoAbsoluteExpiration,
                        Cache.NoSlidingExpiration);
                    //, CacheItemPriority.Normal);
                    //new CacheItemRemovedCallback(WebUtils.CacheItemRemovedCallback));
                }

Every time I set the timeupdated field to getdate(), my code detects that object o is null again, which it should, because it should be dropped from the cache after once it's outdated but why is it working? I have just started following tutorials on SQLCacheDependency, so maybe I missed something while reading them.

EDIT: They're using

SqlCacheDependency dependency = new SqlCacheDependency(command);

and I guess this does no开发者_运维百科t require triggers.

Please feel free to share if you dislike this approach and prefer some other approach.

No, you don't need triggers as such. It's all done on Query Notifications. Have a read through that article, it explains the 3 ways query notifications can be set up using ADO.NET.

It's these query notifications, that notify of changes to the underlying resultset.