Problem with running more asynchronous queries : Have you migrated to version 6.0.5...

Wed, 15 Sep 2010 15:05:30 -700

Author: davidklitzke
Subject: 2151
Posted: 15-Sep-2010 at 3:05pm

Have you migrated to version 6.0.5 yet? This version of DevForce 2010 includes a large number of enhancements and bug fixes. It also contains breaking changes with respect to Asynchronous Operations:
• Exceptions Thrown by Asynchronous Operations Must Be Handled. All asynchronous persistence operation exceptions now conform with Microsoft RIA Service style of exception handling.
• EntityManager.AuthorizedThreadId Property. There is a new AuthorizedThreadId property on the EntityManager that checks to see that the EntityManager is used in a thread-safe manner.
See Release Notes for details.

Problem with running more asynchronous queries : I have noticed the unstable behavior...

Mon, 13 Sep 2010 02:56:07 -700

Author: mpetkovic
Subject: 2151
Posted: 13-Sep-2010 at 2:56am

I have noticed the unstable behavior when I try to work with queries asynchronously.

When I start a new query before the completion of the previous one the application does not show stable behavior (sometimes it crashes and sometimes not).
But If I start the new query after the completion of the previous one the application is then stable.

Please find below the part of code where I pointed out when the problem occurs and when not. The first query is here the employees from the Northwind database and the queries that should be executed after
the first one are put into the method called "then_multiple_async_anonymous_queries_work".

This code comes from a small example project I have made to illustrate this problem. You can get it from me of course if you want to run it.
Any comments/ideas about this problem are welcome.

//Module: BusinessApplicationModule
//file: BusinessApplicationModuleViewModel.cs

private NorthwindIBEntities _mgr = new NorthwindIBEntities();

*****************************************************

//ViewModel constructor:
public BusinessApplicationModuleViewModel() {
     .......

var query = _mgr.Employees;
var op = query.ExecuteAsync();
            op.Completed += (s, args) => {
              if (args.Error == null) {
                args.Results.ForEach(Employees.Add);
                CurrentEmployee = Employees.FirstOrDefault();
                RaisePropertyChanged("CurrentEmployee"); //Consider moving into the property
                //then_multiple_async_anonymous_queries_work(); ///works well
               }
              else
              {
                throw new InvalidOperationException(
                  "Server error during query: " + args.Error.Message);
              }
            };

            then_multiple_async_anonymous_queries_work(); //unstable behaviour

        }
***********************************************************

        public void then_multiple_async_anonymous_queries_work()
        {

                var fetchCount = 0;
                _mgr.Fetching += delegate { fetchCount++; };

                const int iterations = 100;
                int countDownCounter = iterations;

                var locker = new Object();

                Action countDown = (op, results) =>
                {
                    LogFetchingData.Add("In callback for " + op.UserState);
                    lock (locker)
                    {
                        countDownCounter--;
                        if (0 >= countDownCounter)
                        {
                            LogFetchingData.Add("*** Fetch Count = " + fetchCount);

                        }
                    }
                };

                for (var i = 0; i < iterations; i++)
                {
                    _mgr.Employees.Select(emp => new { emp.EmployeeID, emp.Orders.Count })
                      .With(QueryStrategy.DataSourceOnly)
                      .ExecuteAsync(op => countDown((BaseOperation)op, (op.HasError) ? null : (IEnumerable)op.Results), i);
                }
         }

DevForce Community Forum : Problem with running more asynchronous queries

Problem with running more asynchronous queries : Have you migrated to version 6.0.5...

Problem with running more asynchronous queries : I have noticed the unstable behavior...