How do I implement sqldependency with linqtosql?

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Hi ^_^

I want to watch a Configuration table for any changes. This table essentially contains user settings that can be over-ridden by an Admin. If some functionality or access is turned off, then I need to alert the client side (using web sockets).

The issue is that the Admin app and Client app are not in the same solution.

My colleague wants to poll my db (he loves his polls >_<) but I would rather something more elegant.

The Configurations won't be changed very often at all.

So, here is what I have in my Context Ctor:

C#

public Context() // custom Context ctor.
            : base(ConfigurationManager.ConnectionStrings["ebrokerAccess"].ConnectionString)
  {
    SqlDependency.Stop(ConfigurationManager.ConnectionStrings["ebrokerAccess"].ConnectionString);
    SqlDependency.Start(ConfigurationManager.ConnectionStrings["ebrokerAccess"].ConnectionString);

     SqlDependency dep = new SqlDependency((SqlCommand) GetCommand(Configurations.AsQueryable()));

    dep.OnChange += (sender, args) =>
    {
      ConfigurationView.Changed(sender, args);
    };

  }

I have the server agent running and I've enable the broker on the database, but when I change a db value via MSSqlMS, the events don't fire.

Have I completely misunderstood the usage?

Any hints would be helpful ^_^
Thanks
Andy

What I have tried:

I was hoping to use the L2S On[prop]Changing / Changed events, but I gather that they are just PropertyChanged methods within the Context instance.

Posted 23-Jan-17 5:17am

Andy Lanng

Updated 23-Jan-17 8:31am

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Richard Deeming · Accepted Answer · 2017-01-23T08:31:00

It looks like you're missing a vital step:

Detecting Changes with SqlDependency[^]

5. Execute the command using any of the Execute methods of the SqlCommand object. Because the command is bound to the notification object, the server recognizes that it must generate a notification, and the queue information will point to the dependencies queue.

In other words, the notification isn't registered until the associated command is executed. Since you never execute the command, the notification isn't registered, and the change event is never raised.

using (SqlCommand command = (SqlCommand)GetCommand(Configurations.AsQueryable()))
{
    SqlDependency dep = new SqlDependency(command);
    
    dep.OnChange += (sender, args) =>
    {
      ConfigurationView.Changed(sender, args);
    };
    
    using (SqlDataReader reader = command.ExecuteReader())
    {
        // You might need to read the rows here; the documentation isn't clear.
    }
}