InvokeServerMethodAsync is calling the Server Method twice...why?

Problem 1 -

Ah. I see. With regard to the references, sorry I wasn't helpful. One other place we had problems was at deployment. Everything worked fine on the Dev box and the build worked, but the web site on the server was missing some of the needed DLL's. I had to add a bunch of references to the Web Server project to pull in those DLL's. Once that was done, the site started working properly. Not sure if that will help either.

As for the other. We created a Service class that manages the Async stuff and handles the client-server conversation. In this sample, the Deal class can be Promoted. On the client side, the UI Command initiates the deal.Promote(user) method, which instantiates the DealPromotionService and kicks that off. Back on the server, the [AllowRpc} ends up Fetching the Deal with the passed DealId, tells that deal to promote itself, server side, and then returns back to the Service's callback, where the Service then executes an AsyncQuery to refresh the client cache, when that calls back, the Service raises a PromotionCompleted Event that the client side Deal was watching for so that it can do raise the PropertyChanged event that will update the grid/UI.

I don't know if this is a "Good" way to do this, but it is a way and dealt with some of the issues we were having with a long stack of callbacks across projects that just got too confusing and sometimes failed to ever call back.

Here's the code:

public partial class Deal
{
     public void Promote(User user)
     {
          var dps = new DealPromotionService(user, this, PromotionCompletedEventHandler);
     }

     private void PromotionCompletedEventHandler(object o, DealPromotionEventArgs e)
     {
          ...
          OnDealPromoted();
     }

     public event EventHandler<DealPromotionEventArgs> DealPromoted;

     private void OnDealPromoted()
     {
          ...
          if (DealPromoted != null)
               DealPromoted(this, new DealPromotionEventArgs(this, this.Promoted));
     }
}

public class DealPromotionService
{
     public DealPromotionService(User user, Deal deal, EventHandler<DealPromotionEventArgs> promotionCompletedEventHandler)
     {
          ...
          PromoteAsync();
     }

     public event EventHandler<DealPromotionEventArgs> DealPromotionCompleted;

     private void OnDealPromotionCompleted()
     {
          if (DealPromotionCompleted != null)
               DealPromotionCompleted(this, new DealPromotionEventArgs(this.Deal, this.Deal.Promoted));
     }

     private void PromoteAsync()
     {
          var manager = LocalEntityManager.DefaultManager;
          ServerMethodDelegate myDelegate = new ServerMethodDelegate(Promote);
          manager.InvokeServerMethodAsync(myDelegate, PromoteAsyncCallback, this.UserState, this.User.UserId, this.Deal.DealId, this.Deal.SuppressConfirmation); //can't pass entities as parameters in 5.2.1
          //calls back to PromoteAsyncCallback
     }

     [AllowRpc]
     public static string Promote(IPrincipal principal, EntityManager em, params object[] args)
     {
          User user = new User((string)args[0]);
          Deal deal = Deal.Fetch((long)args[1]);
          return Promote(user, deal);
     }

     private static string Promote(User user, Deal deal)
     {
          //server side
          deal.PromoteCore(user);
          return deal.Promoted.ToString(); //return "true" or "false" but boolean does not work as a return type in [AllowRpc]
     }

     private void PromoteAsyncCallback(InvokeServerMethodEventArgs args)
     {
          if (((Guid)args.UserState).Equals(this.UserState))
          {
               //back on the client
               bool success = Convert.ToBoolean(args.Result);
               if (success)
               {
                    //need to refresh
                    FetchAfterPromoteAsync();
               }
               else
               {
                    OnDealPromotionCompleted();
               }
          }
     }

     private void FetchAfterPromoteAsync()
     {
          var qs = new QueryStrategy(FetchStrategy.DataSourceAndCache, MergeStrategy.PreserveChangesUnlessOriginalObsolete);
          var qry = this.Deal.QueryRefreshInPromotion(qs);
          qry.ExecuteAsync(FetchAfterPromoteCallback, this.UserState);
     }

     private void FetchAfterPromoteCallback(EntityFetchedEventArgs<Deal> args)
     {
          if (((Guid)args.UserState).Equals(this.UserState))
          {
               OnDealPromotionCompleted(); //finally, raise this event as the service is finished promoting
          }
     }
}



Edited by skingaby - 28-Sep-2009 at 4:51pm

First of all Skingaby and Kimj, thank you for responding.

Two things:
1) I think it may be a lot easier to call query.ExecuteAsync instead of using this technique; and
2) It sounds like the Silverlight/non-Silverlight versions of the Ideablade dlls may be mixed up.

1) It looks like the ASync method is not doing any server side processing. In my situation, I had a method that called a server side proc that created records which I needed to get back to the client somehow. Even in that situation, we ended up sending an ID back from the Async method and then calling a query.ExecuteAsync in the client side callback.

C2NetDomainModelEntityManager mgr = (C2NetDomainModelEntityManager)eMgr;
    ...
    var customerQ = mgr.EntCustomerSet
        .OrderBy( c => c.p_name )
        .WhereIn( c => c.p_customerID , (from d in customerIDs
                 select d.customerID));
    customerQ.ExecuteAsync(GotCustomers, myToken);

The callback will get a collection of Customer entities in the GotCustomers args.Result property.

2) Make sure the client side Silverlight project is using the .SL versions of the Ideablade dll's and that the server side project is using the regular dll's. I've also had problems with this error when some other project in the solution has mixed up the references. We also had this in the unit tests because although the files were there, the projects in the test run folder weren't finding them. We had to make sure the right files were being copied to the unit test in its deployment configuration.


Edited by skingaby - 28-Sep-2009 at 11:41am

Oh sorry, I didn't realize that Deal was an entity sub-type.  Entities cannot be directly serialized, yet.  You can work around this by returning an EntityCacheState holding the Deal and Contact entities.  In your sample, I'm not sure in which EntityManager Deal and Contact exist, but you can do something like this as the return value from GetADealServer -

     [AllowRpc]
     public static EntityCacheState GetADealServer(IPrincipal principal, EntityManager em, params object[] args)
     {
          var deal =  GetADealCore();
          Logging.LogMessage(String.Format("GetADealServer: Deal ID {0}", deal.DealId));

          return deal.EntityManager.CacheStateManager.GetCacheState();
     }

Deal.GetADealServer is being called twice because of the error - the NotFound error indicates a CommunicationException, and DevForce will attempt a retry of the service call before failing. 

Check the server's debuglog to see if any additional error information was logged, in addition to the InnerException and/or RemoteException properties on the EntityServerException returned to the client.  The Deal type should be both serializable and a "known type".  To make it a known type, implement the marker interface IKnownType or adorn with DiscoverableType(DiscoverableTypeMode.KnownType).