I believe I have found a bug in the feature layer update routing. I am displaying a feature layer with several thousand points and have its mode set to OnDemand. My application has a timer which calls Update and Refresh on the layer to update the display every minute. If I am panning the map and its attempting to update the layer while my timer fires I receive the following error….

System.NullReferenceException was unhandled by user code
Message=Object reference not set to an instance of an object.
at ESRI.ArcGIS.Client.FeatureLayer.update()
at ESRI.ArcGIS.Client.FeatureLayer.Update()
at NGC.WinUI.CADControls.Mapping.AutoRefresh._tmr_Tick(Object sender, EventArgs e) in C:\Users\Mark\Documents\Visual Studio 2010\Projects\XXX\Mapping\AutoRefresh.cs:line 158
at System.Windows.Threading.DispatcherTimer.FireTick(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)

Its appears as if this exception is being throw up from the ESRI code base. Just thought I would drop you a line on this. I am wrapping my timer update code in some exception handling for the time being.