Question

many people seem to have problem in making this work, so i am not new to here, hoping someone would be able to point out what else i can check, this is what i am doing…

Environment : .net 4.0, SQL Server Exrpress 2008 R2

Steps taken to setup the database

CREATE QUEUE WebSiteCacheMessages ;

CREATE SERVICE WebCacheNotifications ON QUEUE WebSiteCacheMessages
  ([http://schemas.microsoft.com/SQL/Notifications/PostQueryNotification]) ;
CREATE ROUTE WebCacheMessagesRoute WITH SERVICE_NAME = 'WebCacheNotifications',ADDRESS = 'LOCAL' ;

EXEC sp_configure 'show advanced options', '1'
GO
RECONFIGURE
GO
EXEC sp_configure 'clr enabled', 1
GO
RECONFIGURE
GO

ALTER DATABASE EFTest SET ENABLE_BROKER WITH ROLLBACK IMMEDIATE
GO     
ALTER AUTHORIZATION ON DATABASE::[EFTEST] TO [domain\user];
GO

Following code to test the notification

     static void Main(string[] args)
        {
            var id = 0;
            string sqlStatement = "SELECT [Id] ,[FirstName],[LastName],[Email] FROM [dbo].[People]";
            string queueName = "WebSiteCacheMessages";
            string connectionString = ConfigurationManager.ConnectionStrings["MyDataContext"].ConnectionString;
            try
            {

                SqlDependency.Start(connectionString, queueName);
                using (var db = new DataContext(connectionString))
                {
                    var person = new Person { Email = "[e-mail]", FirstName = "Testy", LastName = "Tester", HomeAddress = address };
                    db.Persons.Add(person);
                    db.SaveChanges();
                    id = person.Id;
                }
                var dependency = new SqlDependency();
                dependency.AddCommandDependency(new SqlCommand(sqlStatement));
                dependency.OnChange += (o, e) =>
                {
                    Console.WriteLine("Notification called !");
                };
                Console.ReadLine();
            }
            finally
            {
                SqlDependency.Stop(connectionString, queueName);
            }
        }

when i run an update statement on the email column in query window on sql server, i dont see on change event being fired.

There are no events in the event log or database logs, and when i run the following query, i dont see anything

select * from WebSiteCacheMessages -- queue name
select * from sys.transmission_queue

many thanks for reading through this…

Answer 1

You don’t actually execute any command with a SqlDependency on it. You simply associate the SqlDependency with a SqlCommand, but you don’t actually execute the SqlCommand. The Query Notification on server gets created only when you execute the SQL statement. Something like:

var dependency = new SqlDependency();
var SqlCommand cmd = new SqlCommand(sqlStatement);
dependency.AddCommandDependency(cmd);
dependency.OnChange += (o, e) =>
{
    Console.WriteLine("Notification called !");
};

// Executing the command will submit the query notification request
using (SqlDataReader rdr = cmd.ExecuteReader ()) {
   while (rdr.Reader ()) {
      ...
   }
}
Console.Reade ();

Another alternative is to use LinqToCache and query your DataContext.Persons:

var people = from p in db.Persons select new {p.Id, p.LastName, p.FirstName, p.Email};
var peopleCached = people.AsCached("Persons", new QueryCachedOptions () {
  OnInvalidate = (sender, args) => {
    Console.WriteLine("Notification called !");
  }
 });
// Again, the underlying SqlCommand must actually be executed. Iterate the query
foreach (p in peopleCached ) {
 ....
}