SMO : Full-text is not supported on this edition of SQL Server error

I  use sql server 2005 advanced service (i desinstalled sql server 2005 for the advanced edition in order to implement fulltext search).

It works perfectly when i create the FullTextCatalog and Fulltextindex. All the sripts i executed  in sql server management studio work fine.

Now I have finished to developp the application. And i want to check if  the selected database contains a specific catalog, but i got error message "SMO : Full-text is not supported on this edition of SQL Server" althougth the service exists for the server

This is my code source:

srv = new Server(_instancename)
 
if (srv.IsFullTextInstalled == true)//this line return true
{
 Database db = srv.Databases["jorce"];
 if (! db.FullTextCatalogs.Contains("JorceFTCat"))//this line throws exception: "Full-text is not supported on this edition of SQL Server."
 {
 FullTextCatalog ftc = new FullTextCatalog(db, "JorceFTCat");
 ftc.IsDefault = true;
 ftc.Create();
 }
}

I need help. I'm confused