Cannot create unknown type '{}Continue'



I’m getting issue regarding “XamlObjectWriterException”, when run the script.
error message:-
"get_unread_mails has thrown an exception

Source: System.Xaml

Message: Cannot create unknown type ‘{}Continue’.

Exception Type: XamlObjectWriterException

System.Xaml.XamlObjectWriterException: Cannot create unknown type ‘{}Continue’.
at System.Xaml.XamlObjectWriter.WriteStartObject(XamlType xamlType)
at System.Xaml.XamlWriter.WriteNode(XamlReader reader)
at System.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
at System.Activities.XamlIntegration.FuncFactory1.Evaluate() at System.Activities.DynamicActivity.OnInternalCacheMetadata(Boolean createEmptyBindings) at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList1& validationErrors)
at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack1& activitiesRemaining, ActivityCallStack parentChain, IList1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1& validationErrors) at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1& validationErrors)
at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)
at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)
at System.Activities.WorkflowApplication.EnsureInitialized()
at System.Activities.WorkflowApplication.Enqueue(InstanceOperation operation, Boolean push)
at System.Activities.WorkflowApplication.SimpleOperationAsyncResult.Run(TimeSpan timeout)
at System.Activities.WorkflowApplication.BeginRun(AsyncCallback callback, Object state)
at UiPath.Executor.RobotRunner.<>c__DisplayClass51_0.b__0()"

Is there any solution for same?

Missing Activities in UiRobot.exe

Are you trying to run the process created in a different instance into your current system?

Make sure you have all the required activities installed. Looks like ‘Continue’ activity is missing in you current instance of UiPath studio.

Check this:

Rammohan B.


Thanks for replying @Rammohan91,

Continue activity is already installed in uipath activity “Activity>Workflow>control flow>Continue”.

Is there any other possible solution for same issue?


Hello @sams,

Could you please reinstall core package?
attach your workflow



If you run robot.exe -file option in the script, publish at Studio before running.


Thank you! This solved the issue that I had.


awesome response!!!


Hi, Can you please elaborate what do you mean here?


Hi @RiteshJain1411
See Robot Guide here
As of 2018.2, workflows started with this command only work if you had published the containing project at least once beforehand and if the associated project.json file is inside the project folder.


Thanks @tango for the clarification. Appreciate it.


thanks it was helpful.