Blocking Async Queries

Originally posted by kimj

   Hi,

We're writing a Silverlight application using DevForceEF.  We've a number of properties on our classes that are 'derived', meaning they're not directly bound to a column in the database, and they are computed on-the-fly.  Here's a bad example of the type of thing I'm talking about:

public partial class Employee
{
   public bool WorksAlone
   {
      get
      {
         MyEntityManager em = this.EntityManager as MyEntityManager;
         int count = em.Employees.Where(i => i.Location == this.Location).Count();
         return (count == 1);
      }
   }
}

The problem is that Silverlight requires the queries be executed asyncronously, which is fine in most cases, but with respect to a derived property like the example above, it becomes tricky.  Typically we'd use an IAsyncResult and simply wait until the Async call completed before returning the result, but I can't seem to figure out how to do this with DevForce.  The only thing I can seem to make work at all feels really dirty.

public partial class Employee
{
   public bool WorksAlone
   {
      get
      {
         bool result = false;
         MyEntityManager em = this.EntityManager as MyEntityManager;
         if (em != null)
         {
            IEntityQuery<Employee> query = em.Emplyoees.Where(i => i.Location == this.Location);

            worksAloneCompleted = false;
            em.ExecuteQueryAsync(query, new AsyncCompletedCallback<EntityFetchedEventArgs>(WorksAloneCompleted), null);
            while (!worksAloneCompleted);

            result = worksAloneResult;
         }

         return result;
      }
   }

   private bool worksAloneCompleted = false;
   private bool worksAloneResult = false;
   private void WorksAloneCompleted(EntityFetchedEventArgs args)
   {
      int count = 0;
      foreach (var item in args.Result)
         count++;

      worksAloneResult = (count == 1);
      worksAloneCompleted = true;
   }
}

Do you have any other recommendations how to handle this?

Thanks,
Ken