DevForce Community Forum : Async Queries: handling sudden disconnect

DevForce Community Forum : Async Queries: handling sudden disconnect http://www.ideablade.com/forum/ This is an XML content feed of; DevForce Community Forum : DevForce Classic : Async Queries: handling sudden disconnect Wed, 10 Jun 2026 19:11:28 -700 Wed, 19 Nov 2008 17:37:09 -700 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 9.69 360 www.ideablade.com/forum/RSS_post_feed.asp?TID=1004 DevForce Community Forum http://www.ideablade.com/forum/forum_images/IdeaBlade_logo_tm.png http://www.ideablade.com/forum/ Async Queries: handling sudden disconnect : Ah, okay. The GetEntitiesCompletedHandler... http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3647#3647 Author: kimj
Subject: 1004
Posted: 19-Nov-2008 at 5:37pm

Ah, okay. The GetEntitiesCompletedHandler in that tutorial is not checking the GetEntitiesCompletedEventArgs to see if the operation was either cancelled or in error before trying to access the Entities property in ResetAsyncQuery(). These args are a subclass of System.ComponentModel.AsyncCompletedEventArgs, and the event-based pattern indicates that an exception should be raised when trying to access result properties after a cancel or error. Here's more information: http://msdn.microsoft.com/en-us/library/system.componentmodel.asynccompletedeventargs.aspx.

]]> Wed, 19 Nov 2008 17:37:09 -700 http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3647#3647 Async Queries: handling sudden disconnect : I'm using DevForce 3.6.3... http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3645#3645 Author: kjohnson
Subject: 1004
Posted: 19-Nov-2008 at 12:39pm

I'm using DevForce 3.6.3 and testing this scenario in a 2-tier client-server environment. I'll try checking PersistenceServerError handler to see if anything is happening there. As a note, the ResetAsyncQuery() and GetEntitiesCompleted Handler() listed in the exception text are unchanged from the async query tutorial.

************** Exception Text **************
System.InvalidOperationException: Operation has been cancelled.
   at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
   at IdeaBlade.Persistence.GetEntitiesCompletedEventArgs.get_Entities()
   at FrontEnd.XtraMainForm2.ResetAsyncQuery(GetEntitiesCompletedEventArgs e)
   at FrontEnd.XtraMainForm2.GetEntitiesCompletedHandler(Object sender, GetEntitiesCompletedEventArgs e)
   at IdeaBlade.Persistence.PersistenceManager.OnGetEntitiesCompleted(GetEntitiesCompletedEventArgs pArgs)
   at IdeaBlade.Persistence.PersistenceManager.AsyncFetchCompleted(Object pFetchState)

Stack Trace:
   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
   at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
   at System.Threading.ExecutionContext.runTryCode(Object userData)
   at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
   at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at FrontEnd.Program.Main() in \\optimus\Public\Kevin\RealTimePOS\Project Files\FrontEnd\FrontEnd\Program.cs:line 23
]]> Wed, 19 Nov 2008 12:39:09 -700 http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3645#3645 Async Queries: handling sudden disconnect : In theory, a call to PM.CancelAsync()... http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3643#3643 Author: kimj
Subject: 1004
Posted: 19-Nov-2008 at 11:11am

In theory, a call to PM.CancelAsync() should succeed even if the operation was already cancelled -- is this where the exception is thrown?

Depending on the timing of events, it's possible that you could see the connection failure in your PersistenceServerError handler. When the PM detects connection failures it will also enter some retry logic, so that might be confusing things.

What version of DevForce are you using, and are you using WCF or remoting for communications to the BOS? Can you also post the full text and stack trace of the exception?

]]> Wed, 19 Nov 2008 11:11:32 -700 http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3643#3643 Async Queries: handling sudden disconnect : The application I'm currently... http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3641#3641 Author: kjohnson
Subject: 1004
Posted: 19-Nov-2008 at 8:49am

The application I'm currently working on is using asynchronous queries to keep data up to date. I'm also working to get my application to work while disconnected from the network. The problem I am having is concerning sudden loss of network connectivity. I've set up my program to detect when connectivity is lost (loss of network in a client-server, loss of internet in an n-tier), and then cancel the asynchronous queries until connectivity is restored. Unfortunately, I'm getting an error that the 'operation has been canceled' when I cancel the async queries.

I'm canceling and restarting the async queries elsewhere without problems. It is only during this sudden loss of connectivity situation I'm testing that I have a problem. Is there a certain exception being thrown I'm not handling, or would you suggest another way to handle this situation? Or is there documentation I missed that will help?
]]> Wed, 19 Nov 2008 08:49:01 -700 http://www.ideablade.com/forum/forum_posts.asp?TID=1004&PID=3641#3641