When and why threading TimerCallback is triggered?
<p>We have an asp.net application running on IIS6 with .net 2.0 (XP) that calls a web service in a button click event. It would take over 30 mins for web service to finish. But somehow after a certain period of time, usually between 20 ~ 30 mins, asp.net did another postback of button click event which cause problem in our application.</p>

<p>The track stack (see below) shows that postback was triggered by Threading.TimeCallback. Does anyone know why? or anything related to IIS setting?</p>

<p>Appreciated!
Michael</p>

<p>at ASP.platform_workflow_executeworkflow_aspx.ProcessRequest(HttpContext context)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously)
at System.Web.HttpApplication.ApplicationStepManager.ResumeSteps(Exception error)
at System.Web.HttpApplication.ResumeStepsFromThreadPoolThread(Exception error)
at System.Web.HttpApplication.AsyncEventExecutionStep.ResumeStepsWithAssert(Exception error)
at System.Web.HttpApplication.AsyncEventExecutionStep.OnAsyncEventCompletion(IAsyncResult ar)
at System.Web.HttpAsyncResult.Complete(Boolean synchronous, Object result, Exception error, RequestNotificationStatus status)
at System.Web.SessionState.SessionStateModule.PollLockedSessionCallback(Object state)
at System.Threading.ExecutionContext.runTryCode(Object userData)
at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading._TimerCallback.PerformTimerCallback(Object state)</p>
