Question about error and determining the source

Usually I’m pretty good at determining the source of some of the more random and cryptic errors in UiPath, but this most recent one I’ve encountered for some reason is giving me issues… I merely added a few variables to the process and edited one block, the same edits I’ve been making to prior processes because we’re shifting our logging methods for better metrics tracking. I haven’t had any issues until this process and I’ve spent about a day trying to identify the location of the issue…


System.Xaml.XamlObjectWriterException: Cannot set unknown member 'UiPath.Core.Activities.Target.Id'.
   at System.Xaml.XamlObjectWriter.WriteStartMember(XamlMember property)
   at System.Xaml.XamlWriter.WriteNode(XamlReader reader)
   at System.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
   at System.Activities.XamlIntegration.FuncFactory`1.Evaluate()
   at System.Activities.Activity.OnInternalCacheMetadata(Boolean createEmptyBindings)
   at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack`1& activitiesRemaining, ActivityCallStack parentChain, IList`1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
   at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.Validation.ActivityValidationServices.InternalActivityValidationServices.InternalValidate()
   at System.Activities.Validation.ActivityValidationServices.Validate(Activity toValidate, ValidationSettings settings)
   at System.Activities.Presentation.Validation.ValidationService.CoreValidationWork(ValidationReason reason, CancellationToken cancellationToken)

When this error happens?


At all times, it can no longer run due to it and I cannot publish the file obviously because it cannot validate the file.

I suppose this is due to an updated/outdated activity package - currently installed version is expecting different number of propperties than the one used in workflow. Try searching for “Cannot set unknown member”.


hi @mike.vansickle did you find the root cause?