Updated Studio from 2019.10.2 to 2019.10.3 Community and now I have a null reference error on my Custom Library

Hi All,

my studio just updated today to 2019.10.3 and after I opened my previously working project. It is now displaying a validation error. My project has dependency on my other UiPath Library Projects named OdysseyLibrary. It Used to work with no errors prior to the update.

Validation Error:
Issuance.xaml: System.NullReferenceException: Object reference not set to an instance of an object.
at OdysseyLibrary2.NewReceipt.GetImplementation()
at System.Activities.Activity.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, 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)

Would appreciate if anyone can explain why I’m getting this new error, thanks.


Could you please share with us a diag report?


ExecStop.zip (71.5 KB)

Sure, here’s the generated report by DiagTool.

Thank you, we are looking into it.
Could you also share the library?

OdysseyLibrary2.1.0.44.nupkg (193.7 KB)


Hi Alex,

Really appreciate your help on this, I am at a lost on what’s going.

Here is what I did so far to hit this error:

  1. After the studio update I opened the Library Project on Studio 2019.10.3 and republished it even without changing anything, it published successfully without errors.

  2. I then opened my main process project on Studio 2019.10.3 and then updated the OdysseyLibrary2 package to the newly published version.

  3. After the package update I immediately get this error as seen on the attached screenshot

Can you share the library project itself (the one that you want to compile) and the RPAHelperLibrary depdency?

Hi Alex,

I dug a little dipper and did a trial and error, to see which activity in my library is causing this error.

I created a new blank Library Project and I tried to re-create 1 functionality workflow for testing which is my application login workflow.

So one by one I add an activity and publish the library and update it on my main test process project, everything was fine until I added a UiPath.Core.Activities.SelectItem activity and then I hit the same validation error message.

Can you test this on your end? If this is the activity that maybe is causing this because my OdysseyLibrary is full of this activity and maybe that is why I am getting the validation error.

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We managed to reproduce this issue.
Thank you for your feedback.

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Hi Alex,

Thank you, hope this get fixed soon.

For those who have the same issue as I have, you can replace the Select Item Activity with Select Multi Item Activity.

This is a pretty big game-stopper. I recently ran into this issue and thanks @jeffreyhermosa for escalating this.

@alexg do you know if there is a timeline when this will be fixed. And, if this is something that can be resolved through a simple activity package update, or is it going to need to be an Orchestrator update. It is a major headache for us to get IT to make an update to Orchestrator and Studio.

Thanks for this. I will pass this on.

@ClaytonM It should be fixed in Studio 2019.10.4, are you using 2019.10.3 or 2019.10.4 ?

I think 2019.10.3
I’ll see if we can get our team to bump up a version.


@ClaytonM If you can’t bump up version there is also the possibility to switch the compiler with the following flag: “UseLegacyLibraryCompiler”.
You can find more details here: https://docs.uipath.com/studio/docs/about-libraries

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I was linked over to this post from the one I made, and I upgraded to 19.10.4 from 19.10.3 and the issue has been resolved for me