Cannot create unknown type - How to solve?

Hello Ui community,

I’m trying to run a robot from orchestrator and getting the error bellow. Any ideas ?

Info: “Execution error : System.Xaml.XamlObjectWriterException: Cannot create unknown type ‘{clr-namespace:DataTableExtensions.Aggregation;assembly=DataTableExtensions.Activities}SumActivity’.\r\n at System.Xaml.XamlObjectWriter.WriteStartObject(XamlType xamlType)\r\n at System.Xaml.XamlWriter.WriteNode(XamlReader reader)\r\n at System.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)\r\n at System.Activities.XamlIntegration.FuncFactory1.Evaluate()\r\n at System.Activities.DynamicActivity.OnInternalCacheMetadata(Boolean createEmptyBindings)\r\n at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList1& validationErrors)\r\n at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack1&amp; activitiesRemaining, ActivityCallStack parentChain, IList1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)\r\n at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1&amp; validationErrors)\r\n at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList1& validationErrors)\r\n at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)\r\n at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)\r\n at System.Activities.WorkflowApplication.EnsureInitialized()\r\n at System.Activities.WorkflowApplication.Enqueue(InstanceOperation operation, Boolean push)\r\n at System.Activities.WorkflowApplication.SimpleOperationAsyncResult.Run(TimeSpan timeout)\r\n at System.Activities.WorkflowApplication.BeginRun(AsyncCallback callback, Object state)\r\n at UiPath.Executor.RobotRunner.<>c__DisplayClass54_0.<OnInvokeJob>b__0()”

Thanks in advance

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There are two things:

In the NuGet.config file where UiPath is installed on each machine, you will want to include all the activity feeds that you are using like the Gallery or Community feed.

Secondly, on the machine/userId that you are publishing the Workflow from, make sure you have the latest version of the package that is in those feeds. Like in your case, the problem is with the DataTableExtensions, so you would want to make sure that the version you have installed is the latest found in the feed where the package is located. For example, I once had a newer version that was found in the Gallery for the Excel package (no idea why), so I uninstalled the one I had and reinstalled it with the one from the Gallery, then it fixed the issue.

The package dependencies will be found in the publish.json file for the project so if those versions are not found from the feeds in the NuGet.config file then it will give you that error in Orchestrator.

I hope this helps.



Thank you for your reply. Where can i find the NuGet file ?

Where Studio is installed. Probably at “C:\Programs Files (x86)\UiPath”
this will probably need to be edited for each machine.

I’m using in my workflow a community activity (Datatable extensions - Sum), is it possible that the Orchestrator is having problems with just this one activity because it’s community made ?

I could be wrong, but I believe the Orchestrator uses the packages that’s in the publish.json file and looks on the machine that the Robot is running on. So, it’s on a per machine basis, not necessarily with the Orchestrator. If the user id that the Robot is using has a conflict of package version then that error can happen. One thing you can check is the packages that the user id has installed and ensure that they match what is in the publish.json file.

Also, make sure you republish if you correct the packages.


Hey @ClaytonM i solved the problem by picking the package that was missing from the uipath folder in appdata to the folder in C:\ProgramFiles.

Thanks for all your help and time ! :slight_smile:

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